MessageQueue.GetMessageEnumerator Method

Definition

Namespace:

System.Messaging

Assembly:

System.Messaging.dll

Caution

This method returns a MessageEnumerator that implements RemoveCurrent family of methods incorrectly. Please use GetMessageEnumerator2 instead.

Creates an enumerator object for all the messages in the queue. GetMessageEnumerator() is deprecated. GetMessageEnumerator2() should be used instead.

public:
 System::Messaging::MessageEnumerator ^ GetMessageEnumerator();

[System.Obsolete("This method returns a MessageEnumerator that implements RemoveCurrent family of methods incorrectly. Please use GetMessageEnumerator2 instead.")]
public System.Messaging.MessageEnumerator GetMessageEnumerator ();

[<System.Obsolete("This method returns a MessageEnumerator that implements RemoveCurrent family of methods incorrectly. Please use GetMessageEnumerator2 instead.")>]
member this.GetMessageEnumerator : unit -> System.Messaging.MessageEnumerator

Public Function GetMessageEnumerator () As MessageEnumerator

Returns

MessageEnumerator

The MessageEnumerator holding the messages that are contained in the queue.

Attributes

ObsoleteAttribute

Examples

The following code example gets a dynamic list of messages in a queue and counts all messages with the Priority property set to MessagePriority.Lowest.

#using <system.dll>
#using <system.messaging.dll>

using namespace System;
using namespace System::Messaging;
ref class MyNewQueue
{
public:
   void CountLowestPriority()
   {
      
      // Holds the count of Lowest priority messages.
      UInt32 numberItems = 0;
      
      // Connect to a queue.
      MessageQueue^ myQueue = gcnew MessageQueue( ".\\myQueue" );
      
      // Get a cursor into the messages in the queue.
      MessageEnumerator^ myEnumerator = myQueue->GetMessageEnumerator();
      
      // Specify that the messages's priority should be read.
      myQueue->MessageReadPropertyFilter->Priority = true;
      
      // Move to the next message and examine its priority.
      while ( myEnumerator->MoveNext() )
      {
         
         // Increase the count if priority is Lowest.
         if ( myEnumerator->Current->Priority == MessagePriority::Lowest )
                  numberItems++;
      }

      
      // Display final count.
      Console::WriteLine( "Lowest priority messages: {0}", numberItems );
      return;
   }

};

int main()
{
   
   // Create a new instance of the class.
   MyNewQueue^ myNewQueue = gcnew MyNewQueue;
   
   // Output the count of Lowest priority messages.
   myNewQueue->CountLowestPriority();
   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 uses a cursor to step through the
        // messages in a queue and counts the number of
        // Lowest priority messages.
        //**************************************************

        public static void Main()
        {
            // Create a new instance of the class.
            MyNewQueue myNewQueue = new MyNewQueue();

            // Output the count of Lowest priority messages.
            myNewQueue.CountLowestPriority();
                        
            return;
        }

        //**************************************************
        // Iterates through messages in a queue and examines
        // their priority.
        //**************************************************
        
        public void CountLowestPriority()
        {
            // Holds the count of Lowest priority messages.
            uint numberItems = 0;

            // Connect to a queue.
            MessageQueue myQueue = new MessageQueue(".\\myQueue");
    
            // Get a cursor into the messages in the queue.
            MessageEnumerator myEnumerator =
                myQueue.GetMessageEnumerator();

            // Specify that the messages's priority should be read.
            myQueue.MessageReadPropertyFilter.Priority = true;

            // Move to the next message and examine its priority.
            while(myEnumerator.MoveNext())
            {
                // Increase the count if priority is Lowest.
                if(myEnumerator.Current.Priority ==
                    MessagePriority.Lowest)
                    
                    numberItems++;
            }

            // Display final count.
            Console.WriteLine("Lowest priority messages: " +
                numberItems.ToString());
            
            return;
        }
    }
}

Imports System.Messaging

Public Class MyNewQueue


        
        ' Provides an entry point into the application.
        '		 
        ' This example uses a cursor to step through the
        ' messages in a queue and counts the number of 
        ' Lowest priority messages.
        

        Public Shared Sub Main()

            ' Create a new instance of the class.
            Dim myNewQueue As New MyNewQueue()

            ' Output the count of Lowest priority messages.
            myNewQueue.CountLowestPriority()

            Return

        End Sub


        
        ' Iterates through messages in a queue and examines
        ' their priority.
        

        Public Sub CountLowestPriority()

            ' Holds the count of Lowest priority messages.
            Dim numberItems As Int32 = 0

            ' Connect to a queue.
            Dim myQueue As New MessageQueue(".\myQueue")

            ' Get a cursor into the messages in the queue.
            Dim myEnumerator As MessageEnumerator = _
                myQueue.GetMessageEnumerator()

            ' Specify that the messages's priority should be read.
            myQueue.MessageReadPropertyFilter.Priority = True

            ' Move to the next message and examine its priority.
            While myEnumerator.MoveNext()

                ' Increase the count if the priority is Lowest.
                If myEnumerator.Current.Priority = _
                    MessagePriority.Lowest Then
                    numberItems += 1
                End If

            End While

            ' Display final count.
            Console.WriteLine(("Lowest priority messages: " + _
                numberItems.ToString()))

            Return

        End Sub

End Class

Remarks

GetMessageEnumerator creates a dynamic list of all the messages in a queue. You can remove from the queue the message at the enumerator's current position by calling RemoveCurrent for the MessageEnumerator that GetMessageEnumerator returns.

Because the cursor is associated with the dynamic list of messages in the queue, the enumeration reflects any modification you make to the messages in the queue, if the message is beyond the current cursor position. For example, the enumerator can automatically access a lower-priority message placed beyond the cursor's current position, but not a higher-priority message inserted before that position. However, you can reset the enumeration, thereby moving the cursor back to the beginning of the list, by calling Reset for the MessageEnumerator.

The order of the messages in the enumeration reflects their order in the queue, so higher-priority messages will appear before lower-priority ones.

If you want a static snapshot of the messages in the queue rather than a dynamic connection to them, call GetAllMessages. This method returns an array of Message objects, which represent the messages at the time the method was called.

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	Yes
Remote computer and direct format name	Yes

See also

• GetAllMessages()
• GetMessageEnumerator2()
• GetMessageQueueEnumerator()