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Priority Property

Message.Priority Property

Gets or sets the message priority, which determines where in the queue the message is placed.

[Visual Basic]
Public Property Priority As MessagePriority
[C#]
public MessagePriority Priority {get; set;}
[C++]
public: __property MessagePriority get_Priority();
public: __property void set_Priority(MessagePriority);
[JScript]
public function get Priority() : MessagePriority;
public function set Priority(MessagePriority);

Property Value

One of the MessagePriority values, which represent the priority levels of non-transactional messages. The default is Normal.

Exceptions

Exception Type Condition
InvalidOperationException The message queue is filtered to ignore the Priority property.

Remarks

The Priority property affects how Message Queuing handles the message both while it is en route and once it reaches its destination. Higher-priority messages are given preference during routing and inserted toward the front of the destination queue. Messages with the same priority are placed in the queue according to their arrival time.

You can set a meaningful priority only for non-transactional messages. Message Queuing automatically sets the priority for transactional messages to Lowest, which causes transactional message priority to be ignored.

Example

[Visual Basic, C#, C++] The following example sends 2 messages of different priorities to the queue, and retrieves them subsequently.

[Visual Basic] 
Imports System
Imports 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 sends and receives a message from
      ' a queue.
      '**************************************************
      Public Shared Sub Main()
         ' Create a new instance of the class.
         Dim myNewQueue As New MyNewQueue()
         
         ' Send messages to a queue.
         myNewQueue.SendMessage(MessagePriority.Normal, "First Message Body.")
         myNewQueue.SendMessage(MessagePriority.Highest, "Second Message Body.")
         
         ' Receive messages from a queue.
         myNewQueue.ReceiveMessage()
         myNewQueue.ReceiveMessage()
         
         Return
      End Sub 'Main
      
      
      
      '**************************************************
      ' Sends a string message to a queue.
      '**************************************************
      Public Sub SendMessage(priority As MessagePriority, messageBody As String)
         
         ' Connect to a queue on the local computer.
         Dim myQueue As New MessageQueue(".\myQueue")
         
         ' Create a new message.
         Dim myMessage As New Message()
         
         If priority > MessagePriority.Normal Then
            myMessage.Body = "High Priority: " + messageBody
         Else
            myMessage.Body = messageBody
         End If 
         ' Set the priority of the message.
         myMessage.Priority = priority
         
         
         ' Send the Order to the queue.
         myQueue.Send(myMessage)
         
         Return
      End Sub 'SendMessage
      
      
      
      '**************************************************
      ' Receives a message.
      '**************************************************
      Public Sub ReceiveMessage()
         ' Connect to the a queue on the local computer.
         Dim myQueue As New MessageQueue(".\myQueue")
         
         ' Set the queue to read the priority. By default, it
         ' is not read.
         myQueue.MessageReadPropertyFilter.Priority = True
         
         ' Set the formatter to indicate body contains a string.
         myQueue.Formatter = New XmlMessageFormatter(New Type() {GetType(String)})
         
         Try
            ' Receive and format the message. 
            Dim myMessage As Message = myQueue.Receive()
            
            ' Display message information.
            Console.WriteLine(("Priority: " + myMessage.Priority.ToString()))
            Console.WriteLine(("Body: " + myMessage.Body.ToString()))
         
         Catch
         ' Handle Message Queuing exceptions.
         
         ' Handle invalid serialization format.
         Catch e As InvalidOperationException
            Console.WriteLine(e.Message)
         End Try
         
         ' Catch other exceptions as necessary.
         Return
      End Sub 'ReceiveMessage
   End Class 'MyNewQueue
End Namespace 'MyProject

[C#] 
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 sends and receives a message from
        // a queue.
        //**************************************************

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

            // Send messages to a queue.
            myNewQueue.SendMessage(MessagePriority.Normal, "First Message Body.");
            myNewQueue.SendMessage(MessagePriority.Highest, "Second Message Body.");

            // Receive messages from a queue.
            myNewQueue.ReceiveMessage(); 
            myNewQueue.ReceiveMessage();

            return;
        }


        //**************************************************
        // Sends a string message to a queue.
        //**************************************************
        
        public void SendMessage(MessagePriority priority, string messageBody)
        {

            // Connect to a queue on the local computer.
            MessageQueue myQueue = new MessageQueue(".\\myQueue");

            // Create a new message.
            Message myMessage = new Message();

            if(priority > MessagePriority.Normal)
            {
                myMessage.Body = "High Priority: " + messageBody;
            }
            else myMessage.Body = messageBody;

            // Set the priority of the message.
            myMessage.Priority = priority;


            // Send the Order to the queue.
            myQueue.Send(myMessage);

            return;
        }


        //**************************************************
        // Receives a message.
        //**************************************************
        
        public  void ReceiveMessage()
        {
            // Connect to the a queue on the local computer.
            MessageQueue myQueue = new MessageQueue(".\\myQueue");

            // Set the queue to read the priority. By default, it
            // is not read.
            myQueue.MessageReadPropertyFilter.Priority = true;

            // Set the formatter to indicate body contains a string.
            myQueue.Formatter = new XmlMessageFormatter(new Type[]
                {typeof(string)});
            
            try
            {
                // Receive and format the message. 
                Message myMessage =    myQueue.Receive(); 

                // Display message information.
                Console.WriteLine("Priority: " + 
                    myMessage.Priority.ToString());
                Console.WriteLine("Body: " + 
                    myMessage.Body.ToString());
            }
            
            catch (MessageQueueException)
            {
                // Handle Message Queuing exceptions.
            }

            // Handle invalid serialization format.
            catch (InvalidOperationException e)
            {
                Console.WriteLine(e.Message);
            }
            
            // Catch other exceptions as necessary.

            return;
        }
    }
}

[C++] 
#using <mscorlib.dll>
#using <system.dll>
#using <system.messaging.dll>

using namespace System;
using namespace System::Messaging;

__gc class MyNewQueue 
{
public:
    void SendMessage(MessagePriority priority, String* messageBody) 
    {

        // Connect to a queue on the local computer.
        MessageQueue* myQueue = new MessageQueue(S".\\myQueue");

        // Create a new message.
        Message* myMessage = new Message();

        if (priority > MessagePriority::Normal) 
        {
            myMessage->Body = S"High Priority: {0}", messageBody;
        } 
        else myMessage->Body = messageBody;

        // Set the priority of the message.
        myMessage->Priority = priority;

        // Send the Order to the queue.
        myQueue->Send(myMessage);

        return;
    }

public:
    void ReceiveMessage() 
    {
        // Connect to the a queue on the local computer.
        MessageQueue* myQueue = new MessageQueue(S".\\myQueue");

        // Set the queue to read the priority. By default, it
        // is not read.
        myQueue->MessageReadPropertyFilter->Priority = true;

        // Set the formatter to indicate body contains a String*.
        Type* p __gc[] = new Type* __gc[1];
        p[0] = __typeof(String);
        myQueue->Formatter = new XmlMessageFormatter( p );

        try 
        {
            // Receive and format the message. 
            Message* myMessage = myQueue->Receive(); 

            // Display message information.
            Console::WriteLine(S"Priority: {0}", __box(myMessage->Priority));
            Console::WriteLine(S"Body: {0}", myMessage->Body);
        }
        catch (MessageQueueException*) 
        {
            // Handle Message Queuing exceptions.
        }

        // Handle invalid serialization format.
        catch (InvalidOperationException* e) 
        {
            Console::WriteLine(e->Message);
        }
        // Catch other exceptions as necessary.

        return;
    }
};

int main() 
{
    // Create a new instance of the class.
    MyNewQueue* myNewQueue = new MyNewQueue();

    // Send messages to a queue.
    myNewQueue->SendMessage(MessagePriority::Normal, S"First Message Body.");
    myNewQueue->SendMessage(MessagePriority::Highest, S"Second Message Body.");

    // Receive messages from a queue.
    myNewQueue->ReceiveMessage(); 
    myNewQueue->ReceiveMessage();

    return 0;

[JScript] No example is available for JScript. To view a Visual Basic, C#, or C++ example, click the Language Filter button Language Filter in the upper-left corner of the page.

Requirements

Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family

.NET Framework Security: 

See Also

Message Class | Message Members | System.Messaging Namespace | MessagePriority | MessageType | MessageQueue.BasePriority | MessagePriority

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