MessageQueue.EndPeek Method (IAsyncResult)

 
System_CAPS_noteNote

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Completes the specified asynchronous peek operation.

Namespace:   System.Messaging
Assembly:  System.Messaging (in System.Messaging.dll)

public Message EndPeek(
	IAsyncResult asyncResult
)

Parameters

asyncResult
Type: System.IAsyncResult

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

Return Value

Type: System.Messaging.Message

The Message associated with the completed asynchronous operation.

Exception Condition
ArgumentNullException

The asyncResult parameter is null.

ArgumentException

The syntax of the asyncResult parameter is not valid.

MessageQueueException

An error occurred when accessing a Message Queuing method.

When the PeekCompleted event is raised, EndPeek(IAsyncResult) completes the operation that was initiated by the BeginPeek call. To do so, EndPeek(IAsyncResult) peeks the message.

BeginPeek can specify a time-out, which causes the PeekCompleted event to be raised if the time-out occurs before a message appears in the queue. When a time-out occurs without a message arriving in the queue, a subsequent call to EndPeek(IAsyncResult) throws an exception.

EndPeek(IAsyncResult) is used to read the message that caused the PeekCompleted event to be raised.

If you want to continue to asynchronously peek messages, you can again call BeginPeek after calling EndPeek(IAsyncResult).

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

Workgroup mode

Available

Local computer

Yes

Local computer and direct format name

Yes

Remote computer

No

Remote computer and direct format name

Yes

The following code example creates an event handler named MyPeekCompleted, attaches it to the PeekCompleted event handler delegate, and calls BeginPeek to initiate an asynchronous peek operation on the queue that is located at the path ".\myQueue". When a PeekCompleted event is raised, the example peeks the message and writes its body to the screen. The example then calls BeginPeek again to initiate a new asynchronous peek operation.

using System;
using System.Messaging;

namespace MyProject
{
	/// <summary>
	/// Provides a container class for the example.
	/// </summary>
	public class MyNewQueue
	{

		//**************************************************
		// Provides an entry point into the application.
		//		 
		// This example performs asynchronous peek 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 PeekCompleted event.
			myQueue.PeekCompleted += new 
				PeekCompletedEventHandler(MyPeekCompleted);

			// Begin the asynchronous peek operation.
			myQueue.BeginPeek();

			// Do other work on the current thread.

			return;
		}


		//**************************************************
		// Provides an event handler for the PeekCompleted
		// event.
		//**************************************************

		private static void MyPeekCompleted(Object source, 
			PeekCompletedEventArgs asyncResult)
		{
			// Connect to the queue.
			MessageQueue mq = (MessageQueue)source;

			// End the asynchronous peek operation.
			Message m = mq.EndPeek(asyncResult.AsyncResult);

			// Display message information on the screen.
			Console.WriteLine("Message: " + (string)m.Body);

			// Restart the asynchronous peek operation.
			mq.BeginPeek();

			return; 
		}
	}
}

.NET Framework
Available since 1.1
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