MessageQueue.BeginReceive Method (TimeSpan, Cursor, Object, AsyncCallback)
Initiates an asynchronous receive operation that has a specified time-out and uses a specified cursor and a specified state object. The state object provides associated information throughout the lifetime of the operation. This overload receives notification, through a callback, of the identity of the event handler for the operation. The operation is not complete until either a message becomes available in the queue or the time-out occurs.
Assembly: System.Messaging (in System.Messaging.dll)
public IAsyncResult BeginReceive( TimeSpan timeout, Cursor cursor, Object state, AsyncCallback callback )
- Type: System.TimeSpan
A TimeSpan that indicates the interval of time to wait for a message to become available.
- Type: System.Messaging.Cursor
A Cursor that maintains a specific position in the message queue.
- Type: System.Object
A state object, specified by the application, that contains information associated with the asynchronous operation.
When you use this overload, the callback specified in the callback parameter is invoked directly when a message becomes available in the queue or when the specified interval of time has expired; the ReceiveCompleted event is not raised. The other overloads of BeginReceive rely on this component to raise the ReceiveCompleted event.
ReceiveCompleted is also raised if a message already exists in the queue.
To use BeginReceive, create an event handler that processes the results of the asynchronous operation and associate it with your event delegate. BeginReceive initiates an asynchronous receive operation; the MessageQueue is notified, through the raising of the ReceiveCompleted event, when a message arrives in the queue. The MessageQueue can then access the message by calling EndReceive(IAsyncResult) or retrieving the result using the ReceiveCompletedEventArgs.
The BeginReceive method returns immediately, but the asynchronous operation is not completed until the event handler is called.
The IAsyncResult that BeginReceive returns identifies the asynchronous operation that the method started. You can use this IAsyncResult throughout the lifetime of the operation, although you generally do not use it until EndReceive(IAsyncResult) is called. However, if you start several asynchronous operations, you can place their IAsyncResult values in an array and specify whether to wait for all operations or any operation to complete. In this case, use the AsyncWaitHandle property of the IAsyncResult to identify the completed operation.
The state object associates state information with the operation. For example, if you call BeginReceive multiple times to initiate multiple operations, you can identify each operation through a separate state object that you define.
You can also use the state object to pass information across process threads. If a thread is started but the callback is on a different thread in an asynchronous scenario, the state object is marshaled and passed back along with information from the event.
Do not use the asynchronous call BeginReceive with transactions. If you want to perform a transactional asynchronous operation, call BeginPeek, and put the transaction and the (synchronous) Receive method within the event handler you create for the peek operation. Your event handler might contain functionality as shown in the following C# code.
myMessageQueue.BeginTransaction(); myMessageQueue.Receive(); myMessageQueue.CommitTransaction();
The following table shows whether this method is available in various Workgroup modes.
Local computer and direct format name
Remote computer and direct format name