Gets a list of messages from the queue, and specifies how long they should be reserved before becoming visible—and therefore available for deletion. Namespace: Microsoft.WindowsAzure.StorageClient
Assembly: Microsoft.WindowsAzure.StorageClient (in Microsoft.WindowsAzure.StorageClient.dll)
Usage
| Visual Basic |
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Dim instance As CloudQueue Dim messageCount As Integer Dim visibilityTimeout As TimeSpan Dim returnValue As IEnumerable(Of CloudQueueMessage) returnValue = instance.GetMessages(messageCount, visibilityTimeout) |
Syntax
| Visual Basic |
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Public Function GetMessages ( _ messageCount As Integer, _ visibilityTimeout As TimeSpan _ ) As IEnumerable(Of CloudQueueMessage) |
| C# |
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public IEnumerable<CloudQueueMessage> GetMessages ( int messageCount, TimeSpan visibilityTimeout ) |
| C++ |
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public: IEnumerable<CloudQueueMessage^>^ GetMessages ( int messageCount, TimeSpan visibilityTimeout ) |
| J# |
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| JScript |
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Parameters
- messageCount
Type: System.Int32
The number of messages to retrieve.
- visibilityTimeout
Type: System.TimeSpan
The visibility timeout interval.
Return Value
Type: System.Collections.Generic.IEnumerable An enumerable collection of messages.Example
The following code example adds some messages to the queue, retrieves them, and deletes them.
| C# | Copy Code |
|---|---|
static void RetrieveAndDeleteQueueMessages(Uri queueEndpoint, string accountName, string accountKey)
{
//Create service client for credentialed access to the Queue service.
CloudQueueClient queueClient = new CloudQueueClient(queueEndpoint,
new StorageCredentialsAccountAndKey(accountName, accountKey));
//Get a reference to a queue in this storage account.
CloudQueue queue = queueClient.GetQueueReference("myqueue");
//Create the queue if it does not already exist.
queue.CreateIfNotExist();
//Clear any existing messages from the queue.
queue.Clear();
//Create some new messages and add them to the queue.
for (int i = 0; i < 10; i++)
{
CloudQueueMessage msg = new CloudQueueMessage("message" + i.ToString());
queue.AddMessage(msg);
Console.WriteLine("Adding message with content: " + msg.AsString);
}
//Delete five messages from the queue.
foreach(CloudQueueMessage msg in queue.GetMessages(5))
{
Console.WriteLine("Deleting message: " + msg.Id);
queue.DeleteMessage(msg);
}
Console.WriteLine();
//Delete five more messages from the queue.
foreach (CloudQueueMessage msg in queue.GetMessages(5))
{
Console.WriteLine("Deleting message " + msg.Id);
queue.DeleteMessage(msg.Id, msg.PopReceipt);
}
}
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Remarks
The GetMessages method retrieves up to a specified number of messages from the queue. The maximum number of messages that may be retrieved with a single call to GetMessages is 32. If the queue contains no visible messages, an empty list is returned. If the queue contains fewer visible messages than requested, all the visible messages are returned.
After messages have been retrieved, they should be deleted from the queue.
When a message is retrieved from the queue, its NextVisibleTime and PopReceipt properties are updated with values provided by the service. The NextVisibleTime indicates the next time that the message will be available to be read, if it is not deleted by the client that retrieved it. This value is calculated by adding the value of the visibilityTimeout parameter to the time at which the message was retrieved. The maximum value that may be specified for the visibilityTimeout parameter is two hours.
The PopReceipt value indicates that the message has been read and is used to verify that the message being deleted is the same one that was retrieved.
After a client retrieves a message, that message is reserved for deletion until the date and time indicated by the message's NextVisibleTime property, and no other client may retrieve the message during that time interval. If the message is not deleted before the time specified by the NextVisibleTime property, it again becomes visible to other clients. If the message is not subsequently retrieved and deleted by another client, the client that retrieved it can still delete it.
When a message is retrieved for the first time, its DequeueCount property is set to 1. If it is not deleted and is subsequently retrieved again, the DequeueCount property is incremented. The client may use this value to determine how many times a message has been retrieved.