Programming

Connector/Net comprises several classes that are used to connect to the database, execute queries and statements, and manage query results.

The following are the major classes of Connector/Net:

• MySqlCommand: Represents an SQL statement to execute against a MySQL database.

• MySqlCommandBuilder: Automatically generates single-table commands used to reconcile changes made to a DataSet with the associated MySQL database.

• MySqlConnection: Represents an open connection to a MySQL Server database.

• MySqlDataAdapter: Represents a set of data commands and a database connection that are used to fill a data set and update a MySQL database.

• MySqlDataReader: Provides a means of reading a forward-only stream of rows from a MySQL database.

• MySqlException: The exception that is thrown when MySQL returns an error.

• MySqlHelper: Helper class that makes it easier to work with the provider.

• MySqlTransaction: Represents an SQL transaction to be made in a MySQL database.

In the following sections you will learn about some common use cases for Connector/Net, including BLOB handling, date handling, and using Connector/Net with common tools such as Crystal Reports.

Introduction

All interaction between a .NET application and the MySQL server is routed through a MySqlConnection object. Before your application can interact with the server, a MySqlConnection object must be instanced, configured, and opened.

Even when using the MySqlHelper class, a MySqlConnection object is created by the helper class.

In this section, we will describe how to connect to MySQL using the MySqlConnection object.

The MySqlConnection object is configured using a connection string. A connection string contains several key/value pairs, separated by semicolons. Each key/value pair is joined with an equal sign.

The following is a sample connection string:

In this example, the MySqlConnection object is configured to connect to a MySQL server at 127.0.0.1, with a user name of root and a password of 12345. The default database for all statements will be the test database. All other options may be found here: Connection Options.

Note

Using the '@' symbol for parameters is now the preferred approach although the old pattern of using '?' is still supported. Please be aware however that using '@' can cause conflicts when user variables are also used. To help with this situation please see the documentation on the Allow User Variables connection string option, which can be found here: Connection Options. The Old Syntax connection string option has now been deprecated.

Once you have created a connection string it can be used to open a connection to the MySQL server.

The following code is used to create a MySqlConnection object, assign the connection string, and open the connection.

Connector/NET can also connect using the native Windows authentication plugin. See Using the Windows Native Authentication Plugin for further information.

Dim conn As New MySql.Data.MySqlClient.MySqlConnection
Dim myConnectionString as String

myConnectionString = "server=127.0.0.1;" _
            & "uid=root;" _
            & "pwd=12345;" _
            & "database=test;"

Try
  conn.ConnectionString = myConnectionString
  conn.Open()

Catch ex As MySql.Data.MySqlClient.MySqlException
  MessageBox.Show(ex.Message)
End Try

MySql.Data.MySqlClient.MySqlConnection conn;
string myConnectionString;

myConnectionString = "server=127.0.0.1;uid=root;" +
    "pwd=12345;database=test;";

try
{
    conn = new MySql.Data.MySqlClient.MySqlConnection();
    conn.ConnectionString = myConnectionString;
    conn.Open();
}
catch (MySql.Data.MySqlClient.MySqlException ex)
{
    MessageBox.Show(ex.Message);
}

You can also pass the connection string to the constructor of the MySqlConnection class:

Dim myConnectionString as String

myConnectionString = "server=127.0.0.1;" _
              & "uid=root;" _
              & "pwd=12345;" _
              & "database=test;"

Try
    Dim conn As New MySql.Data.MySqlClient.MySqlConnection(myConnectionString)
    conn.Open()
Catch ex As MySql.Data.MySqlClient.MySqlException
   MessageBox.Show(ex.Message)
End Try

MySql.Data.MySqlClient.MySqlConnection conn;
string myConnectionString;

myConnectionString = "server=127.0.0.1;uid=root;" +
    "pwd=12345;database=test;";

try
{
    conn = new MySql.Data.MySqlClient.MySqlConnection(myConnectionString);
    conn.Open();
}
catch (MySql.Data.MySqlClient.MySqlException ex)
{
    MessageBox.Show(ex.Message);
}

Once the connection is open it can be used by the other Connector/Net classes to communicate with the MySQL server.

Because connecting to an external server is unpredictable, it is important to add error handling to your .NET application. When there is an error connecting, the MySqlConnection class will return a MySqlException object. This object has two properties that are of interest when handling errors:

• Message: A message that describes the current exception.

• Number: The MySQL error number.

When handling errors, you can your application's response based on the error number. The two most common error numbers when connecting are as follows:

• 0: Cannot connect to server.

• 1045: Invalid user name and/or password.

The following code shows how to adapt the application's response based on the actual error:

Dim myConnectionString as String

myConnectionString = "server=127.0.0.1;" _
          & "uid=root;" _
          & "pwd=12345;" _
          & "database=test;"

Try
    Dim conn As New MySql.Data.MySqlClient.MySqlConnection(myConnectionString)
    conn.Open()
Catch ex As MySql.Data.MySqlClient.MySqlException
    Select Case ex.Number
        Case 0
            MessageBox.Show("Cannot connect to server. Contact administrator")
        Case 1045
            MessageBox.Show("Invalid username/password, please try again")
    End Select
End Try

MySql.Data.MySqlClient.MySqlConnection conn;
string myConnectionString;

myConnectionString = "server=127.0.0.1;uid=root;" +
    "pwd=12345;database=test;";

try
{
    conn = new MySql.Data.MySqlClient.MySqlConnection(myConnectionString);
    conn.Open();
}
    catch (MySql.Data.MySqlClient.MySqlException ex)
{
    switch (ex.Number)
    {
        case 0:
            MessageBox.Show("Cannot connect to server.  Contact administrator");
        case 1045:
            MessageBox.Show("Invalid username/password, please try again");
    }
}

Important
Note that if you are using multilanguage databases you must specify the character set in the connection string. If you do not specify the character set, the connection defaults to the latin1 charset. You can specify the character set as part of the connection string, for example:

MySqlConnection myConnection = new MySqlConnection("server=127.0.0.1;uid=root;" +
    "pwd=12345;database=test;Charset=latin1;");

The GetSchema() method of the connection object can be used to retrieve schema information about the database currently connected to. The schema information is returned in the form of a DataTable. The schema information is organized into a number of collections. Different forms of the GetSchema() method can be used depending on the information required. There are three forms of the GetSchema() method:

• GetSchema() - This call will return a list of available collections.

• GetSchema(String) - This call returns information about the collection named in the string parameter. If the string is used then a list of all available collections is returned. This is the same as calling GetSchema() without any parameters.

• GetSchema(String, String[]) - In this call the first string parameter represents the collection name, and the second parameter represents a string array of restriction values. Restriction values limit the amount of data that will be returned. Restriction values are explained in more detail in the Microsoft .NET documentation.

The collections can be broadly grouped into two types: collections that are common to all data providers, and collections specific to a particular provider.

Common

The following collections are common to all data providers:

• MetaDataCollections

• DataSourceInformation

• DataTypes

• Restrictions

• ReservedWords

Provider-specific

The following are the collections currently provided by , in addition to the common collections above:

• Databases

• Tables

• Columns

• Users

• Foreign Keys

• IndexColumns

• Indexes

• Foreign Key Columns

• UDF

• Views

• ViewColumns

• Procedure Parameters

• Procedures

• Triggers

Example Code

A list of available collections can be obtained using the following code:

using System;
using System.Data;
using System.Text;
using MySql.Data;
using MySql.Data.MySqlClient;

namespace ConsoleApplication2
{
    class Program
    {

        private static void DisplayData(System.Data.DataTable table)
        {
            foreach (System.Data.DataRow row in table.Rows)
            {
                foreach (System.Data.DataColumn col in table.Columns)
                {
                    Console.WriteLine("{0} = {1}", col.ColumnName, row[col]);
                }
                Console.WriteLine("============================");
            }
        }

        static void Main(string[] args)
        {

            string connStr = "server=localhost;user=root;database=world;port=3306;password=******;";
            MySqlConnection conn = new MySqlConnection(connStr);

            try
            {
                Console.WriteLine("Connecting to MySQL...");
                conn.Open();

                DataTable table = conn.GetSchema("MetaDataCollections");
                //DataTable table = conn.GetSchema("UDF");
                DisplayData(table);

                conn.Close();
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.ToString());
            }
            Console.WriteLine("Done.");
        }
    }
}

Further information on the GetSchema() method and schema collections can be found in the Microsoft .NET documentation.

A MySqlCommand has the CommandText and CommandType properties associated with it. The CommandText will be handled differently depending on the setting of CommandType. CommandType can be one of:

1. Text - A SQL text command (default)

2. StoredProcedure - The name of a Stored Procedure

3. TableDirect - The name of a table (new in Connector/Net 6.2)

The default CommandType, Text, is used for executing queries and other SQL commands. Some example of this can be found in the following section The MySqlCommand Object.

If CommandType is set to StoredProcedure, set CommandText to the name of the Stored Procedure to access.

If CommandType is set to TableDirect, all rows and columns of the named table will be returned when you call one of the Execute methods. In effect, this command performs a SELECT * on the table specified. The CommandText property is set to the name of the table to query. This is illustrated by the following code snippet:

...
MySqlCommand cmd = new MySqlCommand();
cmd.CommandText = "mytable";
cmd.Connection = someConnection;
cmd.CommandType = CommandType.TableDirect;
MySqlDataReader reader = cmd.ExecuteReader();
while (reader.Read())
{
   Console.WriteLn(reader[0], reader[1]...);
}
...

Examples of using the CommandType of StoredProcedure can be found in the section Accessing Stored Procedures with Connector/Net.

Commands can have a timeout associated with them. This is useful as you may not want a situation were a command takes up an excessive amount of time. A timeout can be set using the CommandTimeout property. The following code snippet sets a timeout of one minute:

MySqlCommand cmd = new MySqlCommand();
cmd.CommandTimeout = 60;

The default value is 30 seconds. Avoid a value of 0, which indicates an indefinite wait. To change the default command timeout, use the connection string option Default Command Timeout.

Prior to 6.2, MySqlCommand.CommandTimeout included user processing time, that is processing time not related to direct use of the connector. Timeout was implemented through a .NET Timer, that triggered after CommandTimeout seconds. This timer consumed a thread.

6.2 introduced timeouts that are aligned with how Microsoft handles SqlCommand.CommandTimeout. This property is the cumulative timeout for all network reads and writes during command execution or processing of the results. A timeout can still occur in the MySqlReader.Read method after the first row is returned, and does not include user processing time, only IO operations. The 6.2 implementation uses the underlying stream timeout facility, so is more efficient in that it does not require the additional timer thread as was the case with the previous implementation.

Further details on this can be found in the relevant Microsoft documentation.

The Connector/Net supports connection pooling. This is enabled by default. You can turn it off or adjust its performance characteristics using the connection string options Pooling, Connection Reset, Connection Lifetime, Cache Server Properties, Max Pool Size and Min Pool Size. See Creating a Connector/Net Connection String for further information.

Connection pooling works by keeping the native connection to the server live when the client disposes of a MySqlConnection. Subsequently, if a new MySqlConnection object is opened, it will be created from the connection pool, rather than creating a new native connection. This improves performance.

To work as designed, it is best to let the connection pooling system manage all connections. Do not create a globally accessible instance of MySqlConnection and then manually open and close it. This interferes with the way the pooling works and can lead to unpredictable results or even exceptions.

One approach that simplifies things is to avoid manually creating a MySqlConnection object. Instead use the overloaded methods that take a connection string as an argument. Using this approach, Connector/Net will automatically create, open, close and destroy connections, using the connection pooling system for best performance.

Typed Datasets and the MembershipProvider and RoleProvider classes use this approach. Most classes that have methods that take a MySqlConnection as an argument, also have methods that take a connection string as an argument. This includes MySqlDataAdapter.

Instead of manually creating MySqlCommand objects, you can use the static methods of the MySqlHelper class. These take a connection string as an argument, and they fully support connection pooling.

Starting with 6.2, there is a background job that runs every three minutes and removes connections from pool that have been idle (unused) for more than three minutes. The pool cleanup frees resources on both client and server side. This is because on the client side every connection uses a socket, and on the server side every connection uses a socket and a thread.

Prior to this change, connections were never removed from the pool, and the pool always contained the peak number of open connections. For example, a web application that peaked at 1000 concurrent database connections would consume 1000 threads and 1000 open sockets at the server, without ever freeing up those resources from the connection pool. Note, connections, no matter how old, will not be closed if the number of connections in the pool is less than or equal to the value set by the Min Pool Size connection string parameter.

Connector/Net applications can authenticate to a MySQL server using the Windows Native Authentication Plugin as of Connector/NET 6.4.4 and MySQL 5.5.16. Users who have logged in to Windows can connect from MySQL client programs to the server based on the information in their environment without specifying an additional password. For background and usage information about the authentication plugin, see, [windows-authentication-plugin].

The interface matches the object. To enable, pass in Integrated Security to the connection string with a value of yes or sspi.

Passing in a user ID is optional. When Windows authentication is set up, a MySQL user is created and configured to be used by Windows authentication. By default, this user ID is named auth_windows, but can be defined using a different name. If the default name is used, then passing the user ID to the connection string from Connector/NET is optional, because it will use the auth_windows user. Otherwise, the name must be passed to the using the standard user ID element.

This feature exists with Connector/NET versions 6.4 and above.

Table caching is a feature that can be used to cache slow-changing datasets on the client side. This is useful for applications that are designed to use readers, but still want to minimize trips to the server for slow-changing tables.

This feature is transparent to the application, and is disabled by default.

• To enable table caching, add 'table cache = true' to the connection string.

• Optionally, specify the 'Default Table Cache Age' connection string option, which represents the number of seconds a table is cached before the cached data is discarded. The default value is 60.

• You can turn caching on and off and set caching options at runtime, on a per-command basis.

Introduction

As of MySQL 4.1, it is possible to use prepared statements with Connector/Net. Use of prepared statements can provide significant performance improvements on queries that are executed more than once.

Prepared execution is faster than direct execution for statements executed more than once, primarily because the query is parsed only once. In the case of direct execution, the query is parsed every time it is executed. Prepared execution also can provide a reduction of network traffic because for each execution of the prepared statement, it is necessary only to send the data for the parameters.

Another advantage of prepared statements is that it uses a binary protocol that makes data transfer between client and server more efficient.

To prepare a statement, create a command object and set the .CommandText property to your query.

After entering your statement, call the .Prepare method of the MySqlCommand object. After the statement is prepared, add parameters for each of the dynamic elements in the query.

After you enter your query and enter parameters, execute the statement using the .ExecuteNonQuery(), .ExecuteScalar(), or .ExecuteReader methods.

For subsequent executions, you need only modify the values of the parameters and call the execute method again, there is no need to set the .CommandText property or redefine the parameters.

Dim conn As New MySqlConnection
Dim cmd As New MySqlCommand

conn.ConnectionString = strConnection

Try
   conn.Open()
   cmd.Connection = conn

   cmd.CommandText = "INSERT INTO myTable VALUES(NULL, @number, @text)"
   cmd.Prepare()

   cmd.Parameters.AddWithValue("@number", 1)
   cmd.Parameters.AddWithValue("@text", "One")

   For i = 1 To 1000
       cmd.Parameters("@number").Value = i
       cmd.Parameters("@text").Value = "A string value"

       cmd.ExecuteNonQuery()
     Next
Catch ex As MySqlException
    MessageBox.Show("Error " & ex.Number & " has occurred: " & ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
End Try

MySql.Data.MySqlClient.MySqlConnection conn;
MySql.Data.MySqlClient.MySqlCommand cmd;

conn = new MySql.Data.MySqlClient.MySqlConnection();
cmd = new MySql.Data.MySqlClient.MySqlCommand();

conn.ConnectionString = strConnection;

try
{
    conn.Open();
    cmd.Connection = conn;

    cmd.CommandText = "INSERT INTO myTable VALUES(NULL, @number, @text)";
    cmd.Prepare();

    cmd.Parameters.AddWithValue("@number", 1);
    cmd.Parameters.AddWithValue("@text", "One");

    for (int i=1; i <= 1000; i++)
    {
        cmd.Parameters["@number"].Value = i;
        cmd.Parameters["@text"].Value = "A string value";

        cmd.ExecuteNonQuery();
    }
}
catch (MySql.Data.MySqlClient.MySqlException ex)
{
    MessageBox.Show("Error " + ex.Number + " has occurred: " + ex.Message,
        "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
}

Introduction

MySQL server version 5 and up supports stored procedures with the SQL 2003 stored procedure syntax.

A stored procedure is a set of SQL statements that is stored in the server. Clients make a single call to the stored procedure, passing parameters that can influence the procedure logic and query conditions, rather than issuing individual hardcoded SQL statements.

Stored procedures can be particularly useful in situations such as the following:

• Stored procedures can act as an API or abstraction layer, allowing multiple client applications to perform the same database operations. The applications can be written in different languages and run on different platforms. The applications do not need to hardcode table and column names, complicated queries, and so on. When you extend and optimize the queries in a stored procedure, all the applications that call the procedure automatically receive the benefits.

• When security is paramount, stored procedures keep applications from directly manipulating tables, or even knowing details such as table and column names. Banks, for example, use stored procedures for all common operations. This provides a consistent and secure environment, and procedures can ensure that each operation is properly logged. In such a setup, applications and users would not get any access to the database tables directly, but can only execute specific stored procedures.

Connector/Net supports the calling of stored procedures through the MySqlCommand object. Data can be passed in and out of a MySQL stored procedure through use of the MySqlCommand.Parameters collection.

Note
When you call a stored procedure, the command object makes an additional SELECT call to determine the parameters of the stored procedure. You must ensure that the user calling the procedure has the SELECT privilege on the mysql.proc table to enable them to verify the parameters. Failure to do this will result in an error when calling the procedure.

This section will not provide in-depth information on creating Stored Procedures. For such information, please refer to http://dev.mysql.com/doc/;mysql/en/stored-routines.html.

A sample application demonstrating how to use stored procedures with Connector/Net can be found in the Samples directory of your Connector/Net installation.

Stored procedures in MySQL can be created using a variety of tools. First, stored procedures can be created using the command-line client. Second, stored procedures can be created using workbench. Finally, stored procedures can be created using the .ExecuteNonQuery method of the MySqlCommand object.

Unlike the command-line and GUI clients, you are not required to specify a special delimiter when creating stored procedures in Connector/Net.

To call a stored procedure using Connector/Net, you create a MySqlCommand object and pass the stored procedure name as the .CommandText property. You then set the .CommandType property to CommandType.StoredProcedure.

After the stored procedure is named, you create one MySqlCommand parameter for every parameter in the stored procedure. IN parameters are defined with the parameter name and the object containing the value, OUT parameters are defined with the parameter name and the data type that is expected to be returned. All parameters need the parameter direction defined.

After defining the parameters, you call the stored procedure by using the MySqlCommand.ExecuteNonQuery() method.

Once the stored procedure is called, the values of the output parameters can be retrieved by using the .Value property of the MySqlConnector.Parameters collection.

Note
When a stored procedure is called using MySqlCommand.ExecuteReader, and the stored procedure has output parameters, the output parameters are only set after the MySqlDataReader returned by ExecuteReader is closed.

The following C# example code demonstrates the use of stored procedures. It assumes the database 'employees' has already been created:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using System.Data;
using MySql.Data;
using MySql.Data.MySqlClient;

namespace UsingStoredRoutines
{
    class Program
    {
        static void Main(string[] args)
        {
            MySqlConnection conn = new MySqlConnection();
            conn.ConnectionString = "server=localhost;user=root;database=employees;port=3306;password=******;";
            MySqlCommand cmd = new MySqlCommand();

            try
            {
                Console.WriteLine("Connecting to MySQL...");
                conn.Open();
                cmd.Connection = conn;
                cmd.CommandText = "DROP PROCEDURE IF EXISTS add_emp";
                cmd.ExecuteNonQuery();
                cmd.CommandText = "DROP TABLE IF EXISTS emp";
                cmd.ExecuteNonQuery();
                cmd.CommandText = "CREATE TABLE emp (empno INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY, first_name VARCHAR(20), last_name VARCHAR(20), birthdate DATE)";
                cmd.ExecuteNonQuery();

                cmd.CommandText = "CREATE PROCEDURE add_emp(" +
                                  "IN fname VARCHAR(20), IN lname VARCHAR(20), IN bday DATETIME, OUT empno INT)" +
                                  "BEGIN INSERT INTO emp(first_name, last_name, birthdate) " +
                                  "VALUES(fname, lname, DATE(bday)); SET empno = LAST_INSERT_ID(); END";

                cmd.ExecuteNonQuery();
            }
            catch (MySqlException ex)
            {
                Console.WriteLine ("Error " + ex.Number + " has occurred: " + ex.Message);
            }
            conn.Close();
            Console.WriteLine("Connection closed.");
            try
            {
                Console.WriteLine("Connecting to MySQL...");
                conn.Open();
                cmd.Connection = conn;

                cmd.CommandText = "add_emp";
                cmd.CommandType = CommandType.StoredProcedure;

                cmd.Parameters.AddWithValue("@lname", "Jones");
                cmd.Parameters["@lname"].Direction = ParameterDirection.Input;

                cmd.Parameters.AddWithValue("@fname", "Tom");
                cmd.Parameters["@fname"].Direction = ParameterDirection.Input;

                cmd.Parameters.AddWithValue("@bday", "1940-06-07");
                cmd.Parameters["@bday"].Direction = ParameterDirection.Input;

                cmd.Parameters.AddWithValue("@empno", MySqlDbType.Int32);
                cmd.Parameters["@empno"].Direction = ParameterDirection.Output;

                cmd.ExecuteNonQuery();

                Console.WriteLine("Employee number: "+cmd.Parameters["@empno"].Value);
                Console.WriteLine("Birthday: " + cmd.Parameters["@bday"].Value);
            }
            catch (MySql.Data.MySqlClient.MySqlException ex)
            {
                Console.WriteLine("Error " + ex.Number + " has occurred: " + ex.Message);
            }
            conn.Close();
            Console.WriteLine("Done.");
        }
    }
}

The following code shows the same application in Visual Basic:

One common use for MySQL is the storage of binary data in BLOB columns. MySQL supports four different BLOB data types: TINYBLOB, BLOB, MEDIUMBLOB, and LONGBLOB, all described in [blob] and [storage-requirements].

Data stored in a BLOB column can be accessed using Connector/Net and manipulated using client-side code. There are no special requirements for using Connector/Net with BLOB data.

Simple code examples will be presented within this section, and a full sample application can be found in the Samples directory of the Connector/Net installation.

The first step is using MySQL with BLOB data is to configure the server. Let's start by creating a table to be accessed. In my file tables, I usually have four columns: an AUTO_INCREMENT column of appropriate size (UNSIGNED SMALLINT) to serve as a primary key to identify the file, a VARCHAR column that stores the file name, an UNSIGNED MEDIUMINT column that stores the size of the file, and a MEDIUMBLOB column that stores the file itself. For this example, I will use the following table definition:

CREATE TABLE file(
file_id SMALLINT UNSIGNED AUTO_INCREMENT NOT NULL PRIMARY KEY,
file_name VARCHAR(64) NOT NULL,
file_size MEDIUMINT UNSIGNED NOT NULL,
file MEDIUMBLOB NOT NULL);

After creating a table, you might need to modify the max_allowed_packet system variable. This variable determines how large of a packet (that is, a single row) can be sent to the MySQL server. By default, the server only accepts a maximum size of 1MB from the client application. If you intend to exceed 1MB in your file transfers, increase this number.

The max_allowed_packet option can be modified using MySQL Administrator's Startup Variables screen. Adjust the Maximum permitted option in the Memory section of the Networking tab to an appropriate setting. After adjusting the value, click the Apply Changes button and restart the server using the Service Control screen of MySQL Administrator. You can also adjust this value directly in the my.cnf file (add a line that reads max_allowed_packet=xxM), or use the SET max_allowed_packet=xxM; syntax from within MySQL.

Try to be conservative when setting max_allowed_packet, as transfers of BLOB data can take some time to complete. Try to set a value that will be adequate for your intended use and increase the value if necessary.

To write a file to a database, we need to convert the file to a byte array, then use the byte array as a parameter to an INSERT query.

The following code opens a file using a FileStream object, reads it into a byte array, and inserts it into the file table:

Dim conn As New MySqlConnection
Dim cmd As New MySqlCommand

Dim SQL As String

Dim FileSize As UInt32
Dim rawData() As Byte
Dim fs As FileStream

conn.ConnectionString = "server=127.0.0.1;" _
    & "uid=root;" _
    & "pwd=12345;" _
    & "database=test"

Try
    fs = New FileStream("c:\image.png", FileMode.Open, FileAccess.Read)
    FileSize = fs.Length

    rawData = New Byte(FileSize) {}
    fs.Read(rawData, 0, FileSize)
    fs.Close()

    conn.Open()

    SQL = "INSERT INTO file VALUES(NULL, @FileName, @FileSize, @File)"

    cmd.Connection = conn
    cmd.CommandText = SQL
    cmd.Parameters.AddWithValue("@FileName", strFileName)
    cmd.Parameters.AddWithValue("@FileSize", FileSize)
    cmd.Parameters.AddWithValue("@File", rawData)

    cmd.ExecuteNonQuery()

    MessageBox.Show("File Inserted into database successfully!", _
    "Success!", MessageBoxButtons.OK, MessageBoxIcon.Asterisk)

    conn.Close()
Catch ex As Exception
    MessageBox.Show("There was an error: " & ex.Message, "Error", _
        MessageBoxButtons.OK, MessageBoxIcon.Error)
End Try

MySql.Data.MySqlClient.MySqlConnection conn;
MySql.Data.MySqlClient.MySqlCommand cmd;

conn = new MySql.Data.MySqlClient.MySqlConnection();
cmd = new MySql.Data.MySqlClient.MySqlCommand();

string SQL;
UInt32 FileSize;
byte[] rawData;
FileStream fs;

conn.ConnectionString = "server=127.0.0.1;uid=root;" +
    "pwd=12345;database=test;";

try
{
    fs = new FileStream(@"c:\image.png", FileMode.Open, FileAccess.Read);
    FileSize = fs.Length;

    rawData = new byte[FileSize];
    fs.Read(rawData, 0, FileSize);
    fs.Close();

    conn.Open();

    SQL = "INSERT INTO file VALUES(NULL, @FileName, @FileSize, @File)";

    cmd.Connection = conn;
    cmd.CommandText = SQL;
    cmd.Parameters.AddWithValue("@FileName", strFileName);
    cmd.Parameters.AddWithValue("@FileSize", FileSize);
    cmd.Parameters.AddWithValue("@File", rawData);

    cmd.ExecuteNonQuery();

    MessageBox.Show("File Inserted into database successfully!",
        "Success!", MessageBoxButtons.OK, MessageBoxIcon.Asterisk);

    conn.Close();
}
catch (MySql.Data.MySqlClient.MySqlException ex)
{
    MessageBox.Show("Error " + ex.Number + " has occurred: " + ex.Message,
        "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
}

The Read method of the FileStream object is used to load the file into a byte array which is sized according to the Length property of the FileStream object.

After assigning the byte array as a parameter of the MySqlCommand object, the ExecuteNonQuery method is called and the BLOB is inserted into the file table.

Once a file is loaded into the file table, we can use the MySqlDataReader class to retrieve it.

The following code retrieves a row from the file table, then loads the data into a FileStream object to be written to disk:

Dim conn As New MySqlConnection
Dim cmd As New MySqlCommand
Dim myData As MySqlDataReader
Dim SQL As String
Dim rawData() As Byte
Dim FileSize As UInt32
Dim fs As FileStream

conn.ConnectionString = "server=127.0.0.1;" _
    & "uid=root;" _
    & "pwd=12345;" _
    & "database=test"

SQL = "SELECT file_name, file_size, file FROM file"

Try
    conn.Open()

    cmd.Connection = conn
    cmd.CommandText = SQL

    myData = cmd.ExecuteReader

    If Not myData.HasRows Then Throw New Exception("There are no BLOBs to save")

    myData.Read()

    FileSize = myData.GetUInt32(myData.GetOrdinal("file_size"))
    rawData = New Byte(FileSize) {}

    myData.GetBytes(myData.GetOrdinal("file"), 0, rawData, 0, FileSize)

    fs = New FileStream("C:\newfile.png", FileMode.OpenOrCreate, FileAccess.Write)
    fs.Write(rawData, 0, FileSize)
    fs.Close()

    MessageBox.Show("File successfully written to disk!", "Success!", MessageBoxButtons.OK, MessageBoxIcon.Asterisk)

    myData.Close()
    conn.Close()
Catch ex As Exception
    MessageBox.Show("There was an error: " & ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
End Try

MySql.Data.MySqlClient.MySqlConnection conn;
MySql.Data.MySqlClient.MySqlCommand cmd;
MySql.Data.MySqlClient.MySqlDataReader myData;

conn = new MySql.Data.MySqlClient.MySqlConnection();
cmd = new MySql.Data.MySqlClient.MySqlCommand();

string SQL;
UInt32 FileSize;
byte[] rawData;
FileStream fs;

conn.ConnectionString = "server=127.0.0.1;uid=root;" +
    "pwd=12345;database=test;";

SQL = "SELECT file_name, file_size, file FROM file";

try
{
    conn.Open();

    cmd.Connection = conn;
    cmd.CommandText = SQL;

    myData = cmd.ExecuteReader();

    if (! myData.HasRows)
        throw new Exception("There are no BLOBs to save");

    myData.Read();

    FileSize = myData.GetUInt32(myData.GetOrdinal("file_size"));
    rawData = new byte[FileSize];

    myData.GetBytes(myData.GetOrdinal("file"), 0, rawData, 0, (int)FileSize);

    fs = new FileStream(@"C:\newfile.png", FileMode.OpenOrCreate, FileAccess.Write);
    fs.Write(rawData, 0, (int)FileSize);
    fs.Close();

    MessageBox.Show("File successfully written to disk!",
        "Success!", MessageBoxButtons.OK, MessageBoxIcon.Asterisk);

    myData.Close();
    conn.Close();
}
catch (MySql.Data.MySqlClient.MySqlException ex)
{
    MessageBox.Show("Error " + ex.Number + " has occurred: " + ex.Message,
        "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
}

After connecting, the contents of the file table are loaded into a MySqlDataReader object. The GetBytes method of the MySqlDataReader is used to load the BLOB into a byte array, which is then written to disk using a FileStream object.

The GetOrdinal method of the MySqlDataReader can be used to determine the integer index of a named column. Use of the GetOrdinal method prevents errors if the column order of the SELECT query is changed.

An interceptor is a software design pattern that provides a transparent way to extend or modify some aspect of a program, similar to a user exit. No recompiling is required. With Connector/Net, the interceptors are enabled and disabled by updating the connection string to refer to different sets of interceptor classes that you instantiate.

Connector/Net includes the following interceptor classes:

• The lets you perform additional operations when a program issues a SQL command. For example, you can examine the SQL statement for logging or debugging purposes, substitute your own result set to implement a caching mechanism, and so on. Depending on the use case, your code can supplement the SQL command or replace it entirely.

  The BaseCommandInterceptor class has these methods that you can override:

  Copy

  public virtual bool ExecuteScalar(string sql, ref object returnValue);
  public virtual bool ExecuteNonQuery(string sql, ref int returnValue);
  public virtual bool ExecuteReader(string sql, CommandBehavior behavior, ref MySqlDataReader returnValue);
  public virtual void Init(MySqlConnection connection);

  If your interceptor overrides one of the Execute... methods, set the returnValue output parameter and return true if you handled the event, or false if you did not handle the event. The SQL command is processed normally only when all command interceptors return false.

  The connection passed to the Init method is the connection that is attached to this interceptor.

• The lets you perform additional operations when a program encounters a SQL exception. The exception interception mechanism is modeled after the Connector/J model. You can code an interceptor class and connect it to an existing program without recompiling, and intercept exceptions when they are created. You can then change the exception type and optionally attach information to it. This capability lets you turn on and off logging and debugging code without hardcoding anything in the application. This technique applies to exceptions raised at the SQL level, not to lower-level system or I/O errors.

  You develop an exception interceptor first by creating a subclass of the BaseExceptionInterceptor class. You must override the InterceptException() method. You can also override the Init() method to do some one-time initialization.

  Each exception interceptor has 2 methods:

  Copy

  public abstract Exception InterceptException(Exception exception,
      MySqlConnection connection);
  public virtual void Init(MySqlConnection connection);

  The connection passed to Init() is the connection that is attached to this interceptor.

  Each interceptor is required to override InterceptException and return an exception. It can return the exception it is given, or it can wrap it in a new exception. We currently do not offer the ability to suppress the exception.

Here are examples of using the FQN (fully qualified name) on the connection string:

MySqlConnection c1 = new MySqlConnection(@"server=localhost;pooling=false;
commandinterceptors=CommandApp.MyCommandInterceptor,CommandApp");

MySqlConnection c2 = new MySqlConnection(@"server=localhost;pooling=false;
exceptioninterceptors=ExceptionStackTraceTest.MyExceptionInterceptor,ExceptionStackTraceTest");

In this example, the command interceptor is called CommandApp.MyCommandInterceptor and exists in the CommandApp assembly. The exception interceptor is called ExceptionStackTraceTest.MyExceptionInterceptor and exists in the ExceptionStackTraceTest assembly.

To shorten the connection string, you can register your exception interceptors in your app.config or web.config file like this:

Once you have done that, your connection strings can look like these:

MySqlConnection c1 = new MySqlConnection(@"server=localhost;pooling=false;
commandinterceptors=myC");

MySqlConnection c2 = new MySqlConnection(@"server=localhost;pooling=false;
exceptioninterceptors=myE");

Introduction

MySQL and the .NET languages handle date and time information differently, with MySQL allowing dates that cannot be represented by a .NET data type, such as '0000-00-00 00:00:00'. These differences can cause problems if not properly handled.

The following sections demonstrate how to properly handle date and time information when using Connector/Net.

Connector/Net 6.5 and higher support the fractional seconds feature introduced in MySQL 5.6.4. Fractional seconds could always be specified in a date literal or passed back and forth as parameters and return values, but the fractional part was always stripped off when stored in a table column. In MySQL 5.6.4 and higher, the fractional part is now preserved in data stored and retrieved through SQL. For fractional second handling in MySQL 5.6.4 and higher, see [refman-5.6:fractional-seconds]. For the behavior of fractional seconds prior to MySQL 5.6.4, see [refman-5.5:fractional-seconds].

To use the more precise date and time types, specify a value from 1 to 6 when creating the table column, for example TIME(3) or DATETIME(6), representing the number of digits of precision after the decimal point. Specifying a precision of 0 leaves the fractional part out entirely. In your C# or Visual Basic code, refer to the Millisecond member to retrieve the fractional second value from the MySqlDateTime object returned by the GetMySqlDateTime function. The DateTime object returned by the GetDateTime function also contains the fractional value, but only the first 3 digits.

For related code examples, see the following blog post: https://blogs.oracle.com/MySqlOnWindows/entry/milliseconds_value_support_on_datetime

The differences in date handling can cause problems for developers who use invalid dates. Invalid MySQL dates cannot be loaded into native .NET DateTime objects, including NULL dates.

Because of this issue, .NET DataSet objects cannot be populated by the Fill method of the MySqlDataAdapter class as invalid dates will cause a System.ArgumentOutOfRangeException exception to occur.

The best solution to the date problem is to restrict users from entering invalid dates. This can be done on either the client or the server side.

Restricting invalid dates on the client side is as simple as always using the .NET DateTime class to handle dates. The DateTime class will only allow valid dates, ensuring that the values in your database are also valid. The disadvantage of this is that it is not useful in a mixed environment where .NET and non .NET code are used to manipulate the database, as each application must perform its own date validation.

Users of MySQL 5.0.2 and higher can use the new traditional SQL mode to restrict invalid date values. For information on using the traditional SQL mode, see [server-sql-mode].

Although it is strongly recommended that you avoid the use of invalid dates within your .NET application, it is possible to use invalid dates by means of the MySqlDateTime data type.

The MySqlDateTime data type supports the same date values that are supported by the MySQL server. The default behavior of Connector/Net is to return a .NET DateTime object for valid date values, and return an error for invalid dates. This default can be modified to cause Connector/Net to return MySqlDateTime objects for invalid dates.

To instruct Connector/Net to return a MySqlDateTime object for invalid dates, add the following line to your connection string:

Please note that the use of the MySqlDateTime class can still be problematic. The following are some known issues:

1. Data binding for invalid dates can still cause errors (zero dates like 0000-00-00 do not seem to have this problem).

2. The ToString method return a date formatted in the standard MySQL format (for example, 2005-02-23 08:50:25). This differs from the ToString behavior of the .NET DateTime class.

3. The MySqlDateTime class supports NULL dates, while the .NET DateTime class does not. This can cause errors when trying to convert a MySQLDateTime to a DateTime if you do not check for NULL first.

Because of the known issues, the best recommendation is still to use only valid dates in your application.

The .NET DateTime data type cannot handle NULL values. As such, when assigning values from a query to a DateTime variable, you must first check whether the value is in fact NULL.

When using a MySqlDataReader, use the .IsDBNull method to check whether a value is NULL before making the assignment:

If Not myReader.IsDBNull(myReader.GetOrdinal("mytime")) Then
    myTime = myReader.GetDateTime(myReader.GetOrdinal("mytime"))
Else
    myTime = DateTime.MinValue
End If

if (! myReader.IsDBNull(myReader.GetOrdinal("mytime")))
    myTime = myReader.GetDateTime(myReader.GetOrdinal("mytime"));
else
    myTime = DateTime.MinValue;

NULL values will work in a data set and can be bound to form controls without special handling.

features a bulk loader class that wraps the MySQL statement LOAD DATA INFILE. This gives the ability to load a data file from a local or remote host to the server. The class concerned is MySqlBulkLoader. This class has various methods, the main one being load to cause the specified file to be loaded to the server. Various parameters can be set to control how the data file is processed. This is achieved through setting various properties of the class. For example, the field separator used, such as comma or tab, can be specified, along with the record terminator, such as newline.

The following code shows a simple example of using the MySqlBulkLoader class. First an empty table needs to be created, in this case in the test database:

CREATE TABLE Career (
       Name VARCHAR(100) NOT NULL,
       Age INTEGER,
       Profession VARCHAR(200)
);

A simple tab-delimited data file is also created (it could use any other field delimiter such as comma):

Table Career in Test Database
Name    Age    Profession

Tony    47    Technical Writer
Ana    43    Nurse
Fred    21    IT Specialist
Simon    45    Hairy Biker

Note that with this test file the first three lines will need to be ignored, as they do not contain table data. This can be achieved using the NumberOfLinesToSkip property. This file can then be loaded and used to populate the Career table in the test database:

using System;
using System.Text;
using MySql.Data;
using MySql.Data.MySqlClient;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {

            string connStr = "server=localhost;user=root;database=test;port=3306;password=******;";
            MySqlConnection conn = new MySqlConnection(connStr);

            MySqlBulkLoader bl = new MySqlBulkLoader(conn);
            bl.TableName = "Career";
            bl.FieldTerminator = "\t";
            bl.LineTerminator = "\n";
            bl.FileName = "c:/career_data.txt";
            bl.NumberOfLinesToSkip = 3;

            try
            {
                Console.WriteLine("Connecting to MySQL...");
                conn.Open();

                // Upload data from file
                int count = bl.Load();
                Console.WriteLine(count + " lines uploaded.");

                string sql = "SELECT Name, Age, Profession FROM Career";
                MySqlCommand cmd = new MySqlCommand(sql, conn);
                MySqlDataReader rdr = cmd.ExecuteReader();

                while (rdr.Read())
                {
                    Console.WriteLine(rdr[0] + " -- " + rdr[1] + " -- " + rdr[2]);
                }

                rdr.Close();

                conn.Close();
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.ToString());
            }
            Console.WriteLine("Done.");
        }
    }
}

Further information on LOAD DATA INFILE can be found in [load-data]. Further information on MySqlBulkLoader can be found in the reference documentation that was included with your connector.

6.2 introduced support for .NET 2.0 compatible tracing, using TraceSource objects.

The .NET 2.0 tracing architecture consists of four main parts:

• Source - This is the originator of the trace information. The source is used to send trace messages. The name of the source provided by is mysql.

• Switch - This defines the level of trace information to emit. Typically, this is specified in the app.config file, so that it is not necessary to recompile an application to change the trace level.

• Listener - Trace listeners define where the trace information will be written to. Supported listeners include, for example, the Visual Studio Output window, the Windows Event Log, and the console.

• Filter - Filters can be attached to listeners. Filters determine the level of trace information that will be written. While a switch defines the level of information that will be written to all listeners, a filter can be applied on a per-listener basis, giving finer grained control of trace information.

To use tracing a TraceSource object first needs to be created. To create a TraceSource object in you would use code similar to the following:

To enable trace messages, configure a trace switch. There are three main switch classes, BooleanSwitch, SourceSwitch, and TraceSwitch. Trace switches also have associated with them a trace level enumeration, these are Off, Error, Warning, Info, and Verbose. The following code snippet illustrates creating a switch:

ts.Switch = new SourceSwitch("MySwitch", "Verbose");

This creates a SourceSwitch, called MySwitch, and sets the trace level to Verbose, meaning that all trace messages will be written.

It is convenient to be able to change the trace level without having to recompile the code. This is achieved by specifying the trace level in application configuration file, app.config. You then simply need to specify the desired trace level in the configuration file and restart the application. The trace source is configured within the system.diagnostics section of the file. The following XML snippet illustrates this:

By default, trace information is written to the Output window of Microsoft Visual Studio. There are a wide range of listeners that can be attached to the trace source, so that trace messages can be written out to various destinations. You can also create custom listeners to allow trace messages to be written to other destinations as mobile devices and web services. A commonly used example of a listener is ConsoleTraceListener, which writes trace messages to the console.

To add a listener at run time, use code such as the following:

Then, call methods on the trace source object to generate trace information. For example, the TraceInformation(), TraceEvent(), or TraceData() methods can be used.

The TraceInformation() method simply prints a string passed as a parameter. The TraceEvent() method, as well as the optional informational string, requires a TraceEventType value to be passed to indicate the trace message type, and also an application specific ID. The TraceEventType can have a value of Verbose, Information, Warning, Error, and Critical. Using the TraceData() method you can pass any object, for example an exception object, instead of a message.

To ensure than these generated trace messages gets flushed from the trace source buffers to listeners, invoke the Flush() method. When you are finished using a trace source, call the Close() method. The Close() method first calls Flush(), to ensure any remaining data is written out. It then frees up resources, and closes the listeners associated with the trace source.

ts.TraceInformation("Informational message");
ts.TraceEvent(TraceEventType.Error, 3, "Optional error message");
ts.TraceData(TraceEventType.Error, 3, ex); // pass exception object
ts.Flush();
...
ts.Close();

This section describes how to set up your application to view MySQL trace information.

The first thing you need to do is create a suitable app.config file for your application. An example is shown in the following code:

This ensures a suitable trace source is created, along with a switch. The switch level in this case is set to Verbose to display the maximum amount of information.

In the application the only other step required is to add logging=true to the connection string. An example application could be:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Diagnostics;
using MySql.Data;
using MySql.Data.MySqlClient;
using MySql.Web;


namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {

            string connStr = "server=localhost;user=root;database=world;port=3306;password=******;logging=true;";
            MySqlConnection conn = new MySqlConnection(connStr);
            try
            {
                Console.WriteLine("Connecting to MySQL...");
                conn.Open();

                string sql = "SELECT Name, HeadOfState FROM Country WHERE Continent='Oceania'";
                MySqlCommand cmd = new MySqlCommand(sql, conn);
                MySqlDataReader rdr = cmd.ExecuteReader();

                while (rdr.Read())
                {
                    Console.WriteLine(rdr[0] + " -- " + rdr[1]);
                }

                rdr.Close();

                conn.Close();
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.ToString());
            }
            Console.WriteLine("Done.");
        }
    }
}

This simple application will then generate the following output:

Connecting to MySQL...
mysql Information: 1 : 1: Connection Opened: connection string = 'server=localhost;User Id=root;database=world;port=3306
;password=******;logging=True'
mysql Information: 3 : 1: Query Opened: SHOW VARIABLES
mysql Information: 4 : 1: Resultset Opened: field(s) = 2, affected rows = -1, inserted id = -1
mysql Information: 5 : 1: Resultset Closed. Total rows=272, skipped rows=0, size (bytes)=7058
mysql Information: 6 : 1: Query Closed
mysql Information: 3 : 1: Query Opened: SHOW COLLATION
mysql Information: 4 : 1: Resultset Opened: field(s) = 6, affected rows = -1, inserted id = -1
mysql Information: 5 : 1: Resultset Closed. Total rows=127, skipped rows=0, size (bytes)=4102
mysql Information: 6 : 1: Query Closed
mysql Information: 3 : 1: Query Opened: SET character_set_results=NULL
mysql Information: 4 : 1: Resultset Opened: field(s) = 0, affected rows = 0, inserted id = 0
mysql Information: 5 : 1: Resultset Closed. Total rows=0, skipped rows=0, size (bytes)=0
mysql Information: 6 : 1: Query Closed
mysql Information: 10 : 1: Set Database: world
mysql Information: 3 : 1: Query Opened: SELECT Name, HeadOfState FROM Country WHERE Continent='Oceania'
mysql Information: 4 : 1: Resultset Opened: field(s) = 2, affected rows = -1, inserted id = -1
American Samoa -- George W. Bush
Australia -- Elisabeth II
...
Wallis and Futuna -- Jacques Chirac
Vanuatu -- John Bani
United States Minor Outlying Islands -- George W. Bush
mysql Information: 5 : 1: Resultset Closed. Total rows=28, skipped rows=0, size (bytes)=788
mysql Information: 6 : 1: Query Closed
Done.
mysql Information: 2 : 1: Connection Closed

The first number displayed in the trace message corresponds to the MySQL event type:

The second number displayed in the trace message is the connection count.

Although this example uses the ConsoleTraceListener, any of the other standard listeners could have been used. Another possibility is to create a custom listener that uses the information passed using the TraceEvent method. For example, a custom trace listener could be created to perform active monitoring of the MySQL event messages, rather than simply writing these to an output device.

It is also possible to add listeners to the MySQL Trace Source at run time. This can be done with the following code:

6.3.2 introduced the ability to switch tracing on and off at run time. This can be achieved using the calls MySqlTrace.EnableQueryAnalyzer(string host, int postInterval) and MySqlTrace.DisableQueryAnalyzer(). The parameter host is the URL of the MySQL Enterprise Monitor server to monitor. The parameter postInterval is how often to post the data to MySQL Enterprise Monitor, in seconds.

To build custom listeners that work with the Trace Source, it is necessary to understand the key methods used, and the event data formats used.

The main method involved in passing trace messages is the TraceSource.TraceEvent method. This has the prototype:

public void TraceEvent(
    TraceEventType eventType,
    int id,
    string format,
    params Object[] args
)

This trace source method will process the list of attached listeners and call the listener's TraceListener.TraceEvent method. The prototype for the TraceListener.TraceEvent method is as follows:

public virtual void TraceEvent(
    TraceEventCache eventCache,
    string source,
    TraceEventType eventType,
    int id,
    string format,
    params Object[] args
)

The first three parameters are used in the standard as defined by Microsoft. The last three parameters contain MySQL-specific trace information. Each of these parameters is now discussed in more detail.

int id

This is a MySQL-specific identifier. It identifies the MySQL event type that has occurred, resulting in a trace message being generated. This value is defined by the MySqlTraceEventType public enum contained in the code:

public enum MySqlTraceEventType : int
{
    ConnectionOpened = 1,
    ConnectionClosed,
    QueryOpened,
    ResultOpened,
    ResultClosed,
    QueryClosed,
    StatementPrepared,
    StatementExecuted,
    StatementClosed,
    NonQuery,
    UsageAdvisorWarning,
    Warning,
    Error
}

The MySQL event type also determines the contents passed using the parameter params Object[] args. The nature of the args parameters are described in further detail in the following material.

string format

This is the format string that contains zero or more format items, which correspond to objects in the args array. This would be used by a listener such as ConsoleTraceListener to write a message to the output device.

params Object[] args

This is a list of objects that depends on the MySQL event type, id. However, the first parameter passed using this list is always the driver id. The driver id is a unique number that is incremented each time the connector is opened. This enables groups of queries on the same connection to be identified. The parameters that follow driver id depend of the MySQL event id, and are as follows:

This information will allow you to create custom trace listeners that can actively monitor the MySQL-specific events.

There are certain situations where MySQL will return incorrect metadata about one or more columns. More specifically, the server will sometimes report that a column is binary when it is not and vice versa. In these situations, it becomes practically impossible for the connector to be able to correctly identify the correct metadata.

Some examples of situations that may return incorrect metadata are:

• Execution of SHOW PROCESSLIST. Some of the columns will be returned as binary even though they only hold string data.

• When a temporary table is used to process a resultset, some columns may be returned with incorrect binary flags.

• Some server functions such DATE_FORMAT will incorrectly return the column as binary.

With the availability of BINARY and VARBINARY data types, it is important that we respect the metadata returned by the server. However, we are aware that some existing applications may break with this change, so we are creating a connection string option to enable or disable it. By default, Connector/Net 5.1 respects the binary flags returned by the server. You might need to make small changes to your application to accommodate this change.

In the event that the changes required to your application would be too large, adding 'respect binary flags=false' to your connection string causes the connector to use the prior behavior: any column that is marked as string, regardless of binary flags, will be returned as string. Only columns that are specifically marked as a BLOB will be returned as BLOB.

Treating Binary Blobs As UTF8

MySQL doesn't currently support 4-byte UTF8 sequences. This makes it difficult to represent some multi-byte languages such as Japanese. To try and alleviate this, Connector/Net now supports a mode where binary blobs can be treated as strings.

To do this, you set the 'Treat Blobs As UTF8' connection string keyword to yes. This is all that needs to be done to enable conversion of all binary blobs to UTF8 strings. To convert only some of your BLOB columns, you can make use of the 'BlobAsUTF8IncludePattern' and'BlobAsUTF8ExcludePattern' keywords. Set these to a regular expression pattern that matches the column names to include or exclude respectively.

When the regular expression patterns both match a single column, the include pattern is applied before the exclude pattern. The result, in this case, would be that the column would be excluded. Also, be aware that this mode does not apply to columns of type BINARY or VARBINARY and also do not apply to nonbinary BLOB columns.

Currently, this mode only applies to reading strings out of MySQL. To insert 4-byte UTF8 strings into blob columns, use the .NET Encoding.GetBytes function to convert your string to a series of bytes. You can then set this byte array as a parameter for a BLOB column.

Introduction

Crystal Reports is a common tool used by Windows application developers to perform reporting and document generation. In this section we will show how to use Crystal Reports XI with MySQL and Connector/Net.

When creating a report in Crystal Reports there are two options for accessing the MySQL data while designing your report.

The first option is to use Connector/ODBC as an ADO data source when designing your report. You will be able to browse your database and choose tables and fields using drag and drop to build your report. The disadvantage of this approach is that additional work must be performed within your application to produce a data set that matches the one expected by your report.

The second option is to create a data set in VB.NET and save it as XML. This XML file can then be used to design a report. This works quite well when displaying the report in your application, but is less versatile at design time because you must choose all relevant columns when creating the data set. If you forget a column you must re-create the data set before the column can be added to the report.

The following code can be used to create a data set from a query and write it to disk:

Dim myData As New DataSet
Dim conn As New MySqlConnection
Dim cmd As New MySqlCommand
Dim myAdapter As New MySqlDataAdapter

conn.ConnectionString = "server=127.0.0.1;" _
    & "uid=root;" _
    & "pwd=12345;" _
    & "database=world"

Try
    conn.Open()
    cmd.CommandText = "SELECT city.name AS cityName, city.population AS CityPopulation, " _
        & "country.name, country.population, country.continent " _
        & "FROM country, city ORDER BY country.continent, country.name"
    cmd.Connection = conn

    myAdapter.SelectCommand = cmd
    myAdapter.Fill(myData)

    myData.WriteXml("C:\dataset.xml", XmlWriteMode.WriteSchema)
Catch ex As Exception
    MessageBox.Show(ex.Message, "Report could not be created", MessageBoxButtons.OK, MessageBoxIcon.Error)
End Try

DataSet myData = new DataSet();
MySql.Data.MySqlClient.MySqlConnection conn;
MySql.Data.MySqlClient.MySqlCommand cmd;
MySql.Data.MySqlClient.MySqlDataAdapter myAdapter;

conn = new MySql.Data.MySqlClient.MySqlConnection();
cmd = new MySql.Data.MySqlClient.MySqlCommand();
myAdapter = new MySql.Data.MySqlClient.MySqlDataAdapter();

conn.ConnectionString = "server=127.0.0.1;uid=root;" +
  "pwd=12345;database=test;";

try
{
  cmd.CommandText = "SELECT city.name AS cityName, city.population AS CityPopulation, " +
  "country.name, country.population, country.continent " +
  "FROM country, city ORDER BY country.continent, country.name";
  cmd.Connection = conn;

  myAdapter.SelectCommand = cmd;
  myAdapter.Fill(myData);

  myData.WriteXml(@"C:\dataset.xml", XmlWriteMode.WriteSchema);
}
catch (MySql.Data.MySqlClient.MySqlException ex)
{
  MessageBox.Show(ex.Message, "Report could not be created",
  MessageBoxButtons.OK, MessageBoxIcon.Error);
}

The resulting XML file can be used as an ADO.NET XML datasource when designing your report.

If you choose to design your reports using Connector/ODBC, it can be downloaded from dev.mysql.com.

For most purposes, the Standard Report wizard helps with the initial creation of a report. To start the wizard, open Crystal Reports and choose the option from the File menu.

The wizard first prompts you for a data source. If you use Connector/ODBC as your data source, use the OLEDB provider for ODBC option from the OLE DB (ADO) tree instead of the ODBC (RDO) tree when choosing a data source. If using a saved data set, choose the ADO.NET (XML) option and browse to your saved data set.

The remainder of the report creation process is done automatically by the wizard.

After the report is created, choose the Report Options... entry of the File menu. Un-check the Save Data With Report option. This prevents saved data from interfering with the loading of data within our application.

To display a report we first populate a data set with the data needed for the report, then load the report and bind it to the data set. Finally we pass the report to the crViewer control for display to the user.

The following references are needed in a project that displays a report:

• CrystalDecisions.CrystalReports.Engine

• CrystalDecisions.ReportSource

• CrystalDecisions.Shared

• CrystalDecisions.Windows.Forms

The following code assumes that you created your report using a data set saved using the code shown in Creating a Data Source, and have a crViewer control on your form named myViewer.

Imports CrystalDecisions.CrystalReports.Engine
Imports System.Data
Imports MySql.Data.MySqlClient

Dim myReport As New ReportDocument
Dim myData As New DataSet
Dim conn As New MySqlConnection
Dim cmd As New MySqlCommand
Dim myAdapter As New MySqlDataAdapter

conn.ConnectionString = _
    "server=127.0.0.1;" _
    & "uid=root;" _
    & "pwd=12345;" _
    & "database=test"

Try
    conn.Open()

    cmd.CommandText = "SELECT city.name AS cityName, city.population AS CityPopulation, " _
        & "country.name, country.population, country.continent " _
        & "FROM country, city ORDER BY country.continent, country.name"
    cmd.Connection = conn

    myAdapter.SelectCommand = cmd
    myAdapter.Fill(myData)

    myReport.Load(".\world_report.rpt")
    myReport.SetDataSource(myData)
    myViewer.ReportSource = myReport
Catch ex As Exception
    MessageBox.Show(ex.Message, "Report could not be created", MessageBoxButtons.OK, MessageBoxIcon.Error)
End Try

using CrystalDecisions.CrystalReports.Engine;
using System.Data;
using MySql.Data.MySqlClient;

ReportDocument myReport = new ReportDocument();
DataSet myData = new DataSet();
MySql.Data.MySqlClient.MySqlConnection conn;
MySql.Data.MySqlClient.MySqlCommand cmd;
MySql.Data.MySqlClient.MySqlDataAdapter myAdapter;

conn = new MySql.Data.MySqlClient.MySqlConnection();
cmd = new MySql.Data.MySqlClient.MySqlCommand();
myAdapter = new MySql.Data.MySqlClient.MySqlDataAdapter();

conn.ConnectionString = "server=127.0.0.1;uid=root;" +
    "pwd=12345;database=test;";

try
{
    cmd.CommandText = "SELECT city.name AS cityName, city.population AS CityPopulation, " +
        "country.name, country.population, country.continent " +
        "FROM country, city ORDER BY country.continent, country.name";
    cmd.Connection = conn;

    myAdapter.SelectCommand = cmd;
    myAdapter.Fill(myData);

    myReport.Load(@".\world_report.rpt");
    myReport.SetDataSource(myData);
    myViewer.ReportSource = myReport;
}
catch (MySql.Data.MySqlClient.MySqlException ex)
{
    MessageBox.Show(ex.Message, "Report could not be created",
        MessageBoxButtons.OK, MessageBoxIcon.Error);
}

A new data set it generated using the same query used to generate the previously saved data set. Once the data set is filled, a ReportDocument is used to load the report file and bind it to the data set. The ReportDocument is the passed as the ReportSource of the crViewer.

This same approach is taken when a report is created from a single table using Connector/ODBC. The data set replaces the table used in the report and the report is displayed properly.

When a report is created from multiple tables using Connector/ODBC, a data set with multiple tables must be created in our application. This enables each table in the report data source to be replaced with a report in the data set.

We populate a data set with multiple tables by providing multiple SELECT statements in our MySqlCommand object. These SELECT statements are based on the SQL query shown in Crystal Reports in the Database menu's Show SQL Query option. Assume the following query:

SELECT `country`.`Name`, `country`.`Continent`, `country`.`Population`, `city`.`Name`, `city`.`Population`
FROM `world`.`country` `country` LEFT OUTER JOIN `world`.`city` `city` ON `country`.`Code`=`city`.`CountryCode`
ORDER BY `country`.`Continent`, `country`.`Name`, `city`.`Name`

This query is converted to two SELECT queries and displayed with the following code:

Imports CrystalDecisions.CrystalReports.Engine
Imports System.Data
Imports MySql.Data.MySqlClient

Dim myReport As New ReportDocument
Dim myData As New DataSet
Dim conn As New MySqlConnection
Dim cmd As New MySqlCommand
Dim myAdapter As New MySqlDataAdapter

conn.ConnectionString = "server=127.0.0.1;" _
    & "uid=root;" _
    & "pwd=12345;" _
    & "database=world"

Try
    conn.Open()
    cmd.CommandText = "SELECT name, population, countrycode FROM city ORDER BY countrycode, name; " _
        & "SELECT name, population, code, continent FROM country ORDER BY continent, name"
    cmd.Connection = conn

    myAdapter.SelectCommand = cmd
    myAdapter.Fill(myData)

    myReport.Load(".\world_report.rpt")
    myReport.Database.Tables(0).SetDataSource(myData.Tables(0))
    myReport.Database.Tables(1).SetDataSource(myData.Tables(1))
    myViewer.ReportSource = myReport
Catch ex As Exception
    MessageBox.Show(ex.Message, "Report could not be created", MessageBoxButtons.OK, MessageBoxIcon.Error)
End Try

using CrystalDecisions.CrystalReports.Engine;
using System.Data;
using MySql.Data.MySqlClient;

ReportDocument myReport = new ReportDocument();
DataSet myData = new DataSet();
MySql.Data.MySqlClient.MySqlConnection conn;
MySql.Data.MySqlClient.MySqlCommand cmd;
MySql.Data.MySqlClient.MySqlDataAdapter myAdapter;

conn = new MySql.Data.MySqlClient.MySqlConnection();
cmd = new MySql.Data.MySqlClient.MySqlCommand();
myAdapter = new MySql.Data.MySqlClient.MySqlDataAdapter();

conn.ConnectionString = "server=127.0.0.1;uid=root;" +
    "pwd=12345;database=test;";

try
{
    cmd.CommandText = "SELECT name, population, countrycode FROM city ORDER " +
        "BY countrycode, name; <literal xmlns="http://ddue.schemas.microsoft.com/authoring/2003/5">SELECT</literal> name, population, code, continent FROM " +
        "country ORDER BY continent, name";
    cmd.Connection = conn;

    myAdapter.SelectCommand = cmd;
    myAdapter.Fill(myData);

    myReport.Load(@".\world_report.rpt");
    myReport.Database.Tables(0).SetDataSource(myData.Tables(0));
    myReport.Database.Tables(1).SetDataSource(myData.Tables(1));
    myViewer.ReportSource = myReport;
}
catch (MySql.Data.MySqlClient.MySqlException ex)
{
    MessageBox.Show(ex.Message, "Report could not be created",
        MessageBoxButtons.OK, MessageBoxIcon.Error);
}

It is important to order the SELECT queries in alphabetic order, as this is the order the report will expect its source tables to be in. One SetDataSource statement is needed for each table in the report.

This approach can cause performance problems because Crystal Reports must bind the tables together on the client-side, which will be slower than using a pre-saved data set.

provides support for the ASP.NET 2.0 provider model. This model enables application developers to focus on the business logic of their application instead of having to recreate such boilerplate items as membership and roles support.

supplies the following providers:

• Membership Provider

• Role Provider

• Profile Provider

• Session State Provider ( 6.1 and later)

The following tables show the supported providers, their default provider and the corresponding MySQL provider.

Membership Provider

Role Provider

Profile Provider

SessionState Provider

Note
The MySQL Session State provider uses slightly different capitalization on the class name compared to the other MySQL providers.

Installing The Providers

The installation of Connector/Net 5.1 or later will install the providers and register them in your machine's .NET configuration file, machine.config. The additional entries created will result in the system.web section appearing similar to the following code:

<system.web>
  <processModel autoConfig="true" />
  <httpHandlers />
  <membership>
    <providers>
      <add name="AspNetSqlMembershipProvider" type="System.Web.Security.SqlMembershipProvider, System.Web, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" connectionStringName="LocalSqlServer" enablePasswordRetrieval="false" enablePasswordReset="true" requiresQuestionAndAnswer="true" applicationName="/" requiresUniqueEmail="false" passwordFormat="Hashed" maxInvalidPasswordAttempts="5" minRequiredPasswordLength="7" minRequiredNonalphanumericCharacters="1" passwordAttemptWindow="10" passwordStrengthRegularExpression="" />
      <add name="MySQLMembershipProvider" type="MySql.Web.Security.MySQLMembershipProvider, MySql.Web, Version=6.1.1.0, Culture=neutral, PublicKeyToken=c5687fc88969c44d" connectionStringName="LocalMySqlServer" enablePasswordRetrieval="false" enablePasswordReset="true" requiresQuestionAndAnswer="true" applicationName="/" requiresUniqueEmail="false" passwordFormat="Clear" maxInvalidPasswordAttempts="5" minRequiredPasswordLength="7" minRequiredNonalphanumericCharacters="1" passwordAttemptWindow="10" passwordStrengthRegularExpression="" />
    </providers>
  </membership>
  <profile>
    <providers>
      <add name="AspNetSqlProfileProvider" connectionStringName="LocalSqlServer" applicationName="/" type="System.Web.Profile.SqlProfileProvider, System.Web, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" />
      <add name="MySQLProfileProvider" type="MySql.Web.Profile.MySQLProfileProvider, MySql.Web, Version=6.1.1.0, Culture=neutral, PublicKeyToken=c5687fc88969c44d" connectionStringName="LocalMySqlServer" applicationName="/" />
    </providers>
  </profile>
  <roleManager>
    <providers>
      <add name="AspNetSqlRoleProvider" connectionStringName="LocalSqlServer" applicationName="/" type="System.Web.Security.SqlRoleProvider, System.Web, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" />
      <add name="AspNetWindowsTokenRoleProvider" applicationName="/" type="System.Web.Security.WindowsTokenRoleProvider, System.Web, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" />
      <add name="MySQLRoleProvider" type="MySql.Web.Security.MySQLRoleProvider, MySql.Web, Version=6.1.1.0, Culture=neutral, PublicKeyToken=c5687fc88969c44d" connectionStringName="LocalMySqlServer" applicationName="/" />
    </providers>
  </roleManager>
</system.web>

Each provider type can have multiple provider implementations. The default provider can also be set here using the defaultProvider attribute, but usually this is set in the web.config file either manually or by using the ASP.NET configuration tool.

At time of writing, the MySqlSessionStateStore is not added to machine.config at install time, and so add the following:

<sessionState>
  <providers>
    <add name="MySqlSessionStateStore" type="MySql.Web.SessionState.MySqlSessionStateStore, MySql.Web, Version=6.1.1.0, Culture=neutral, PublicKeyToken=c5687fc88969c44d" connectionStringName="LocalMySqlServer" applicationName="/" />
  </providers>
</sessionState>

The SessionState Provider uses the customProvider attribute, rather than defaultProvider, to set the provider as the default. A typical web.config file might contain:

<system.web>
     <membership defaultProvider="MySQLMembershipProvider" />
     <roleManager defaultProvider="MySQLRoleProvider" />
     <profile defaultProvider="MySQLProfileProvider" />
     <sessionState customProvider="MySqlSessionStateStore" />
     <compilation debug="false">
       ...

This sets the MySQL Providers as the defaults to be used in this web application.

The providers are implemented in the file mysql.web.dll and this file can be found in your installation folder. There is no need to run any type of SQL script to set up the database schema, as the providers create and maintain the proper schema automatically.

Using The Providers

The easiest way to start using the providers is to use the ASP.NET configuration tool that is available on the Solution Explorer toolbar when you have a website project loaded.

In the web pages that open, you can select the MySQL membership and roles providers by picking a custom provider for each area.

When the provider is installed, it creates a dummy connection string named LocalMySqlServer. Although this has to be done so that the provider will work in the ASP.NET configuration tool, you override this connection string in your web.config file. You do this by first removing the dummy connection string and then adding in the proper one, as shown in the following example:

<connectionStrings>
  <remove name="LocalMySqlServer"/>
  <add name="LocalMySqlServer" connectionString="server=xxx;uid=xxx;pwd=xxx;database=xxx;"/>
</connectionStrings>

Note the database to connect to must be specified.

Rather than manually editing configuration files, consider using the MySQL Website Configuration tool to configure your desired provider setup. From 6.1.1 onwards, all providers can be selected and configured from this wizard. The tool modifies your website.config file to the desired configuration. A tutorial on doing this is available in the following section MySQL Website Configuration Tool.

A tutorial demonstrating how to use the Membership and Role Providers can be found in the following section Tutorial: ASP.NET Membership and Role Provider.

Deployment

To use the providers on a production server, distribute the MySql.Data and the MySql.Web assemblies, and either register them in the remote systems Global Assembly Cache or keep them in your application's bin/ directory.

.NET applications operate under a given trust level. Normal desktop applications operate under full trust, while web applications that are hosted in shared environments are normally run under the partial trust level (also known as ). Some hosting providers host shared applications in their own app pools and allow the application to run under full trust, but this configuration is relatively rare. The Connector/Net support for partial trust has improved over time to simplify the configuration and deployment process for hosting providers.

Connector/Net 6.5 fully enables our provider to run in a partial trust environment when the library is installed in the Global Assembly Cache (GAC). The new MySqlClientPermission class, derived from the .NET DBDataPermission class, helps to simplify the permission setup.

Starting from 6.5 you can use the Connector/Net library inside any medium-trust level environment without any issue.

The following list shows steps and code fragments needed to run a Connector/Net application in a partial trust environment. For illustration purposes, we use the Pipe Connections protocol in this example.

1. Configure the MySQL server to accept pipe connections, by adding the --enable-named-pipe option on the command line. If you need more information about this, see [windows-installation].

2. Confirm that the hosting provider has installed the Connector/Net library (MySql.Data.dll) in the GAC.

3. Optionally, the hosting provider can avoid granting permissions globally by using the new MySqlClientPermission class in the trust policies. (The alternative is to globally enable the permissions System.Net.SocketPermission, System.Security.Permissions.ReflectionPermission, System.Net.DnsPermission, and System.Security.Permissions.SecurityPermission.)

4. Create a simple web application using Visual Studio 2010.

5. Add the reference in your application for the MySql.Data.MySqlClient library.

6. Edit your web.config file so that your application runs using a Medium trust level:

7. Add the MySql.Data.MySqlClient namespace to your server-code page.

8. Define the connection string:

   Copy

   MySqlConnectionStringBuilder myconnString = new MySqlConnectionStringBuilder("server=localhost;User Id=root;database=test;"   );
             myconnString.PipeName = "MySQL55";
             myconnString.ConnectionProtocol = MySqlConnectionProtocol.Pipe;

9. Define the MySqlConnection to use:

   Copy

   MySqlConnection myconn = new MySqlConnection(myconnString.ConnectionString);
   myconn.Open();

10. Retrieve some data from your tables:

    Copy

    MySqlCommand cmd = new MySqlCommand("Select * from products", myconn);
    MySqlDataAdapter da = new MySqlDataAdapter(cmd);
    DataSet1 tds = new DataSet1();
    da.Fill(tds, tds.Tables[0].TableName);
    GridView1.DataSource = tds;
    GridView1.DataBind();
    myconn.Close()

11. Run the program. It should execute successfully, without requiring any special code or encountering any security problems.

Starting with these versions, Connector/Net can be used under partial trust hosting that has been modified to allow the use of sockets for communication. By default, partial trust does not include SocketPermission. Connector/Net uses sockets to talk with the MySQL server so the hosting provider must create a new trust level that is an exact clone of partial trust but that has the following permissions added:

• System.Net.SocketPermission

• System.Security.Permissions.ReflectionPermission

• System.Net.DnsPermission

• System.Security.Permissions.SecurityPermission

Connector/Net versions prior to 5.0.8 and 5.1.3 were not compatible with partial trust hosting.