Message::Id Property

 

Gets the message's identifier.

Namespace:   System.Messaging
Assembly:  System.Messaging (in System.Messaging.dll)

public:
[MessagingDescriptionAttribute("MsgId")]
property String^ Id {
	String^ get();
}

Property Value

Type: System::String^

The message's unique identifier, which is generated by Message Queuing.

Exception Condition
InvalidOperationException

The message has not been sent. This property can only be read on messages retrieved from a queue.

-or-

The message queue is filtered to ignore the Id property.

Message Queuing generates a message identifier when the message is sent. The identifier is composed of 20 bytes and includes two items: the machine Guid of the sending computer and a unique identifier for the message on the computer. The combination of the two items produces a message identifier that is unique on the network.

Message Queuing generates message identifiers for all messages—including acknowledgment and report messages. An acknowledgment message is generally sent by Message Queuing in reaction to the arrival or failure of an original, sent message. You can find the Id property value of the original message in the CorrelationId property of an acknowledgment message.

You can also use the Id property when sending a response message to a response queue. To include the identifier of the original message in a response message, set the CorrelationId property of the response message to the Id property of the original message. The application reading the response message can then use the correlation identifier of the response message to identify the original message.

The following code example sends and receives a message containing an order to and from a queue. It specifically requests a positive acknowledgment when the original message reaches or is retrieved from the queue.

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

using namespace System;
using namespace System::Messaging;
ref class MyNewQueue
{
public:
   static void CreateQueue( String^ queuePath )
   {
      try
      {
         if (  !MessageQueue::Exists( queuePath ) )
         {
            MessageQueue::Create( queuePath );
         }
         else
         {
            Console::WriteLine(  "{0} already exists.", queuePath );
         }
      }
      catch ( MessageQueueException^ e ) 
      {
         Console::WriteLine( e->Message );
      }

   }

   void SendMessage()
   {
      // Connect to a queue on the local computer.
      MessageQueue^ myQueue = gcnew MessageQueue( ".\\myQueue" );

      // Create a new message.
      Message^ myMessage = gcnew Message( "Original Message" );
      myMessage->AdministrationQueue = gcnew MessageQueue( ".\\myAdministrationQueue" );
      myMessage->AcknowledgeType = (AcknowledgeTypes)(AcknowledgeTypes::PositiveReceive | AcknowledgeTypes::PositiveArrival);

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

   String^ ReceiveMessage()
   {
      // Connect to the a queue on the local computer.
      MessageQueue^ myQueue = gcnew MessageQueue( ".\\myQueue" );
      myQueue->MessageReadPropertyFilter->CorrelationId = true;
      array<Type^>^p = gcnew array<Type^>(1);
      p[ 0 ] = String::typeid;
      myQueue->Formatter = gcnew XmlMessageFormatter( p );
      String^ returnString = nullptr;
      try
      {
         // Receive and format the message. 
         Message^ myMessage = myQueue->Receive();

         // Display message information.
         Console::WriteLine( "____________________________________________" );
         Console::WriteLine( "Original message information--" );
         Console::WriteLine( "Body: {0}", myMessage->Body );
         Console::WriteLine( "Id: {0}", myMessage->Id );
         Console::WriteLine( "____________________________________________" );
         returnString = myMessage->Id;
      }
      catch ( MessageQueueException^ ) 
      {
         // Handle Message Queuing exceptions.
      }
      // Handle invalid serialization format.
      catch ( InvalidOperationException^ e ) 
      {
         Console::WriteLine( e->Message );
      }

      // Catch other exceptions as necessary.
      return returnString;
   }

   void ReceiveAcknowledgment( String^ messageId, String^ queuePath )
   {
      bool found = false;
      MessageQueue^ queue = gcnew MessageQueue( queuePath );
      queue->MessageReadPropertyFilter->CorrelationId = true;
      queue->MessageReadPropertyFilter->Acknowledgment = true;
      try
      {
         while ( queue->PeekByCorrelationId( messageId ) != nullptr )
         {
            Message^ myAcknowledgmentMessage = queue->ReceiveByCorrelationId( messageId );

            // Output acknowledgment message information. The correlation Id is identical
            // to the id of the original message.
            Console::WriteLine( "Acknowledgment Message Information--" );
            Console::WriteLine( "Correlation Id: {0}", myAcknowledgmentMessage->CorrelationId );
            Console::WriteLine( "Id: {0}", myAcknowledgmentMessage->Id );
            Console::WriteLine( "Acknowledgment Type: {0}", myAcknowledgmentMessage->Acknowledgment );
            Console::WriteLine( "____________________________________________" );
            found = true;
         }
      }
      catch ( InvalidOperationException^ e ) 
      {
         // This exception would be thrown if there is no (further) acknowledgment message
         // with the specified correlation Id. Only output a message if there are no messages;
         // not if the loop has found at least one.
         if ( found == false )
         {
            Console::WriteLine( e->Message );
         }

         // Handle other causes of invalid operation exception.
      }

   }

};

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

   // Create new queues.
   MyNewQueue::CreateQueue( ".\\myQueue" );
   MyNewQueue::CreateQueue( ".\\myAdministrationQueue" );

   // Send messages to a queue.
   myNewQueue->SendMessage();

   // Receive messages from a queue.
   String^ messageId = myNewQueue->ReceiveMessage();

   // Receive acknowledgment message.
   if ( messageId != nullptr )
   {
      myNewQueue->ReceiveAcknowledgment( messageId, ".\\myAdministrationQueue" );
   }

   return 0;
}

.NET Framework
Available since 1.1
Return to top
Show: