MessageQueue.PeekCompleted Event
Definition
Important
Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.
Occurs when a message is read without being removed from the queue. This is a result of the asynchronous operation, BeginPeek().
public:
event System::Messaging::PeekCompletedEventHandler ^ PeekCompleted;[System.Messaging.MessagingDescription("MQ_PeekCompleted")]
public event System.Messaging.PeekCompletedEventHandler PeekCompleted;[<System.Messaging.MessagingDescription("MQ_PeekCompleted")>]
member this.PeekCompleted : System.Messaging.PeekCompletedEventHandler Public Custom Event PeekCompleted As PeekCompletedEventHandler Event Type
- Attributes
Examples
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.dll>
#using <system.messaging.dll>
using namespace System;
using namespace System::Messaging;
// This example performs asynchronous peek operation
// processing.
//*************************************************
ref class MyNewQueue
{
public:
// Provides an event handler for the PeekCompleted
// event.
static void MyPeekCompleted( Object^ source, PeekCompletedEventArgs^ asyncResult )
{
// Connect to the queue.
MessageQueue^ mq = dynamic_cast<MessageQueue^>(source);
// End the asynchronous peek operation.
Message^ m = mq->EndPeek( asyncResult->AsyncResult );
// Display message information on the screen.
Console::WriteLine( "Message: {0}", static_cast<String^>(m->Body) );
// Restart the asynchronous peek operation.
mq->BeginPeek();
return;
}
};
// Provides an entry point into the application.
//
int main()
{
// Create an instance of MessageQueue. Set its formatter.
MessageQueue^ myQueue = gcnew MessageQueue( ".\\myQueue" );
array<Type^>^p = gcnew array<Type^>(1);
p[ 0 ] = String::typeid;
myQueue->Formatter = gcnew XmlMessageFormatter( p );
// Add an event handler for the PeekCompleted event.
myQueue->PeekCompleted += gcnew PeekCompletedEventHandler( MyNewQueue::MyPeekCompleted );
// Begin the asynchronous peek operation.
myQueue->BeginPeek();
// Do other work on the current thread.
return 0;
}
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;
}
}
}
Imports System.Messaging
' Provides a container class for the example.
Public Class MyNewQueue
' Provides an entry point into the application.
'
' This example performs asynchronous peek 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 PeekCompleted event.
AddHandler myQueue.PeekCompleted, AddressOf _
MyPeekCompleted
' Begin the asynchronous peek operation.
myQueue.BeginPeek()
' Do other work on the current thread.
Return
End Sub
'**************************************************
' Provides an event handler for the PeekCompleted
' event.
'**************************************************
Private Shared Sub MyPeekCompleted(ByVal [source] As _
[Object], ByVal asyncResult As PeekCompletedEventArgs)
' Connect to the queue.
Dim mq As MessageQueue = CType([source], MessageQueue)
' End the asynchronous peek operation.
Dim m As Message = mq.EndPeek(asyncResult.AsyncResult)
' Display message information on the screen.
Console.WriteLine(("Message: " + CStr(m.Body)))
' Restart the asynchronous peek operation.
mq.BeginPeek()
Return
End Sub
End Class
Remarks
BeginPeek is used in asynchronous processing to raise the PeekCompleted event when a message is available in the queue.
EndPeek(IAsyncResult) is used to complete the operation initiated by a call to BeginPeek and peek the message when the PeekCompleted event is raised.
When you create a PeekCompletedEventHandler delegate, you identify the method that will handle the event. To associate the event with your event handler, add an instance of the delegate to the event. The event handler is called whenever the event occurs, unless you remove the delegate. For more information about event handler delegates, see Handling and Raising Events.
