Begins an asynchronous operation to get 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 callback As AsyncCallback Dim state As Object Dim returnValue As IAsyncResult returnValue = instance.BeginGetMessages(messageCount, visibilityTimeout, callback, state) |
Syntax
| Visual Basic |
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Public Function BeginGetMessages ( _ messageCount As Integer, _ visibilityTimeout As TimeSpan, _ callback As AsyncCallback, _ state As Object _ ) As IAsyncResult |
| C# |
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public IAsyncResult BeginGetMessages ( int messageCount, TimeSpan visibilityTimeout, AsyncCallback callback, Object state ) |
| C++ |
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public: IAsyncResult^ BeginGetMessages ( int messageCount, TimeSpan visibilityTimeout, AsyncCallback^ callback, Object^ state ) |
| 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.
- 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.IAsyncResultAn 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.