MessageQueue.EndPeek(IAsyncResult) 方法

定义

完成指定的异步查看操作。

public:
 System::Messaging::Message ^ EndPeek(IAsyncResult ^ asyncResult);
public System.Messaging.Message EndPeek (IAsyncResult asyncResult);
member this.EndPeek : IAsyncResult -> System.Messaging.Message
Public Function EndPeek (asyncResult As IAsyncResult) As Message

参数

asyncResult
IAsyncResult

IAsyncResult 标识要完成的异步查看操作,并且从它检索最终结果。

返回

Message

Message 与已完成的异步操作关联。

例外

asyncResult 参数为 null

asyncResult 参数的语法无效。

访问“消息队列”方法时出错。

示例

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。 然后,该示例再次调用 BeginPeek 以启动新的异步速览操作。

#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

PeekCompleted引发事件时,EndPeek(IAsyncResult)完成由调用启动的操作BeginPeek。 为此, EndPeek(IAsyncResult) 请速览消息。

BeginPeek 可以指定超时,这会导致 PeekCompleted 在消息出现在队列中之前超时时引发该事件。 出现超时时,没有到达队列的消息,后续调用 EndPeek(IAsyncResult) 将引发异常。

EndPeek(IAsyncResult) 用于读取导致 PeekCompleted 引发事件的消息。

如果要继续异步查看消息,可以在调用后再次调用BeginPeekEndPeek(IAsyncResult)

下表显示了此方法是否在各种工作组模式下可用。

工作组模式 可用
本地计算机
本地计算机和直接格式名称
远程计算机
远程计算机和直接格式名称

适用于

另请参阅