CloudQueue.BeginGetMessages Method (Int32, AsyncCallback, Object)

Storage Client Library NET API

[This topic is part of the Microsoft Azure Storage Client Library 1.7, which has been deprecated. See Storage Client Library for the latest version.]

Begins an asynchronous operation to get messages from the queue.

Namespace: Microsoft.WindowsAzure.StorageClient
Assembly: Microsoft.WindowsAzure.StorageClient (in Microsoft.WindowsAzure.StorageClient.dll)

Usage

Visual Basic
Dim instance As CloudQueue
Dim messageCount As Integer
Dim callback As AsyncCallback
Dim state As Object
Dim returnValue As IAsyncResult

returnValue = instance.BeginGetMessages(messageCount, callback, state)

Syntax

Visual Basic
Public Function BeginGetMessages ( _
	messageCount As Integer, _
	callback As AsyncCallback, _
	state As Object _
) As IAsyncResult
C#
public IAsyncResult BeginGetMessages (
	int messageCount,
	AsyncCallback callback,
	Object state
)
C++
public:
IAsyncResult^ BeginGetMessages (
	int messageCount, 
	AsyncCallback^ callback, 
	Object^ state
)
J#
JScript

Parameters

messageCount

Type: System.Int32

The number of messages to retrieve.

callback

Type: System.AsyncCallback

The callback delegate that will receive notification when the asynchronous operation completes.

state

Type: System.Object

A user-defined object that will be passed to the callback delegate.

Return Value

Type: System.IAsyncResult

An IAsyncResult that references the asynchronous operation.

Remarks

The BeginGetMessages method begins an operation to retrieve a specified number of messages from the queue. The maximum number of messages that may be retrieved with a single call to BeginGetMessages is 32.

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; by default this value is set to 30 seconds after the time that the message was retrieved.

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.


Thread Safety

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Platforms

Development Platforms

Windows Vista, Windows 7, Windows Server 2008, Windows 8.1, Windows Server 2012 R2, Windows 8 and Windows Server 2012

See Also