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MessageQueue.EndReceive Method

Completes the specified asynchronous receive operation.

[Visual Basic]
Public Function EndReceive( _
   ByVal asyncResult As IAsyncResult _
) As Message
[C#]
public Message EndReceive(
 IAsyncResult asyncResult
);
[C++]
public: Message* EndReceive(
 IAsyncResult* asyncResult
);
[JScript]
public function EndReceive(
   asyncResult : IAsyncResult
) : Message;

Parameters

asyncResult
The IAsyncResult that identifies the asynchronous receive operation to finish, and from which to retrieve an end result.

Return Value

The Message associated with the completed asynchronous operation.

Exceptions

Exception Type Condition
ArgumentNullException The asyncResult parameter is a null reference (Nothing in Visual Basic).
ArgumentException The syntax of the asyncResult parameter is invalid.
MessageQueueException An error occurred when accessing a Message Queuing API.

Remarks

When the ReceiveCompleted event is raised, EndReceive completes the operation that was initiated by the BeginReceive call. To do so, EndReceive receives the message.

BeginReceive can specify a time-out, which causes the ReceiveCompleted event to be raised if the time-out occurs before a message appears in the queue. In this case, the IsCompleted property of the asyncResult parameter is set to true, but no message is associated with the operation. When a time-out occurs without a message arriving in the queue, a subsequent call to EndReceive throws an exception.

EndReceive is used to read (removing from the queue) the message that caused the ReceiveCompleted event to be raised.

If you want to continue to asynchronously receive messages, you can again call BeginReceive after calling EndReceive.

The following table shows whether this method is available in various Workgroup modes.

Workgroup Mode Available
Local computer Yes
Local computer + direct format name Yes
Remote computer No
Remote computer + direct format name Yes

Example

[Visual Basic, C#, C++] The following example chains asynchronous requests. It assumes there is a queue on the local computer called "myQueue". The Main function begins the asynchronous operation that is handled by the MyReceiveCompleted routine. MyReceiveCompleted processes the current message and begins a new asynchronous receive operation.

[Visual Basic] 
Imports System
Imports System.Messaging
Imports System.Threading

Namespace MyProject

    '/ <summary>
    '/ Provides a container class for the example.
    '/ </summary>
    Public Class MyNewQueue

        ' Define static class members.
        Private Shared signal As New ManualResetEvent(False)
        Private Shared count As Integer = 0


        '**************************************************
        ' Provides an entry point into the application.
        '         
        ' This example performs asynchronous receive
        ' operation processing.
        '**************************************************

        Public Shared Sub Main()
            ' Create an instance of MessageQueue. Set its formatter.
            Dim myQueue As New MessageQueue(".\myQueue")
            myQueue.Formatter = New XmlMessageFormatter(New Type() _
                {GetType([String])})

            ' Add an event handler for the ReceiveCompleted event.
            AddHandler myQueue.ReceiveCompleted, AddressOf _
                MyReceiveCompleted

            ' Begin the asynchronous receive operation.
            myQueue.BeginReceive()

            signal.WaitOne()

            ' Do other work on the current thread.

            Return

        End Sub 'Main


        '***************************************************
        ' Provides an event handler for the ReceiveCompleted
        ' event.
        '***************************************************

        Private Shared Sub MyReceiveCompleted(ByVal [source] As _
            [Object], ByVal asyncResult As ReceiveCompletedEventArgs)

            Try
                ' Connect to the queue.
                Dim mq As MessageQueue = CType([source], MessageQueue)

                ' End the asynchronous receive operation.
                Dim m As Message = _
                    mq.EndReceive(asyncResult.AsyncResult)

                count += 1
                If count = 10 Then
                    signal.Set()
                End If

                ' Restart the asynchronous receive operation.
                mq.BeginReceive()

            Catch
                ' Handle sources of MessageQueueException.

                ' Handle other exceptions.

            End Try

            Return

        End Sub 'MyReceiveCompleted

    End Class 'MyNewQueue
End Namespace 'MyProject

[C#] 
using System;
using System.Messaging;
using System.Threading;

namespace MyProject
{
    /// <summary>
    /// Provides a container class for the example.
    /// </summary>
    public class MyNewQueue
    {
        // Define static class members.
        static ManualResetEvent signal = new ManualResetEvent(false);
        static int count = 0;

        //**************************************************
        // Provides an entry point into the application.
        //         
        // This example performs asynchronous receive
        // operation processing.
        //**************************************************

        public static void Main()
        {
            // Create an instance of MessageQueue. Set its formatter.
            MessageQueue myQueue = new MessageQueue(".\\myQueue");
            myQueue.Formatter = new XmlMessageFormatter(new Type[]
                {typeof(String)});

            // Add an event handler for the ReceiveCompleted event.
            myQueue.ReceiveCompleted += 
                new ReceiveCompletedEventHandler(MyReceiveCompleted);
            
            // Begin the asynchronous receive operation.
            myQueue.BeginReceive();

            signal.WaitOne();
            
            // Do other work on the current thread.

            return;
        }


        //***************************************************
        // Provides an event handler for the ReceiveCompleted
        // event.
        //***************************************************
        
        private static void MyReceiveCompleted(Object source, 
            ReceiveCompletedEventArgs asyncResult)
        {
            try
            {
                // Connect to the queue.
                MessageQueue mq = (MessageQueue)source;

                // End the asynchronous receive operation.
                Message m = mq.EndReceive(asyncResult.AsyncResult);
                
                count += 1;
                if (count == 10)
                {
                    signal.Set();
                }

                // Restart the asynchronous receive operation.
                mq.BeginReceive();
            }
            catch(MessageQueueException)
            {
                // Handle sources of MessageQueueException.
            }
            
            // Handle other exceptions.
            
            return; 
        }
    }
}

[C++] 
#using <mscorlib.dll>
#using <system.dll>
#using <system.messaging.dll>

using namespace System;
using namespace System::Messaging;
using namespace System::Threading;

__gc class MyNewQueue 
{
public:
    // Define static class members.
    static ManualResetEvent* signal = new ManualResetEvent(false);
    static int count = 0;

    // Provides an event handler for the ReceiveCompleted
    // event.

public:
    static void MyReceiveCompleted(Object* source, 
        ReceiveCompletedEventArgs* asyncResult) 
    {
        try 
        {
            // Connect to the queue.
            MessageQueue* mq = dynamic_cast<MessageQueue*>(source);

            // End the asynchronous receive operation.
            mq->EndReceive(asyncResult->AsyncResult);

            count += 1;
            if (count == 10) 
            {
                signal->Set();
            }

            // Restart the asynchronous receive operation.
            mq->BeginReceive();
        } 
        catch (MessageQueueException*) 
        {
            // Handle sources of MessageQueueException.
        }

        // Handle other exceptions.

        return; 
    }
};

// Provides an entry point into the application.
//         
// This example performs asynchronous receive
// operation processing.

int main()
{
    // Create an instance of MessageQueue. Set its formatter.
    MessageQueue* myQueue = new MessageQueue(S".\\myQueue");

    Type* p __gc[] = new Type* __gc[1];
    p[0] = __typeof(String);
    myQueue->Formatter = new XmlMessageFormatter( p );

    // Add an event handler for the ReceiveCompleted event.
    myQueue->ReceiveCompleted += new ReceiveCompletedEventHandler(0, MyNewQueue::MyReceiveCompleted);

    // Begin the asynchronous receive operation.
    myQueue->BeginReceive();

    MyNewQueue::signal->WaitOne();

    // Do other work on the current thread.

    return 0;
}

[JScript] No example is available for JScript. To view a Visual Basic, C#, or C++ example, click the Language Filter button Language Filter in the upper-left corner of the page.

Requirements

Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family

.NET Framework Security: 

See Also

MessageQueue Class | MessageQueue Members | System.Messaging Namespace | BeginReceive | ReceiveCompleted | EndPeek

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