MessageQueue.PeekCompleted 事件

定义

在消息未从队列移除的情况下读取该消息时发生。Occurs when a message is read without being removed from the queue. 这是异步操作 BeginPeek() 的结果。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 

事件类型

PeekCompletedEventHandler
属性

示例

下面的代码示例创建一个名为的事件处理程序 MyPeekCompleted ,将其附加到 PeekCompleted 事件处理程序委托,并调用 BeginPeek 以对位于路径 ".\myQueue" 的队列启动异步查看操作。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". PeekCompleted引发事件时,该示例将扫视消息,并将其正文写入屏幕。When a PeekCompleted event is raised, the example peeks the message and writes its body to the screen. 然后,该示例 BeginPeek 再次调用以启动新的异步查看操作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

注解

BeginPeek 当队列中有消息时,将在异步处理过程中用于引发 PeekCompleted 事件。BeginPeek is used in asynchronous processing to raise the PeekCompleted event when a message is available in the queue.

EndPeek(IAsyncResult) 用于完成通过调用启动的操作 BeginPeek ,并在引发事件时查看消息 PeekCompletedEndPeek(IAsyncResult) is used to complete the operation initiated by a call to BeginPeek and peek the message when the PeekCompleted event is raised.

创建 PeekCompletedEventHandler 委托时,需要标识将处理该事件的方法。When you create a PeekCompletedEventHandler delegate, you identify the method that will handle the event. 若要将事件与事件处理程序关联,请将该委托的一个实例添加到事件中。To associate the event with your event handler, add an instance of the delegate to the event. 除非移除了该委托,否则每当发生该事件时就会调用事件处理程序。The event handler is called whenever the event occurs, unless you remove the delegate. 有关事件处理程序委托的详细信息,请参阅 处理和引发事件For more information about event handler delegates, see Handling and Raising Events.

适用于

另请参阅