MessageQueue.Exists(String) Method

Definition

Namespace:

System.Messaging

Assembly:

System.Messaging.dll

Determines whether a Message Queuing queue exists at the specified path.

public:
 static bool Exists(System::String ^ path);

public static bool Exists (string path);

static member Exists : string -> bool

Public Shared Function Exists (path As String) As Boolean

Parameters

path

String

The location of the queue to find.

Returns

Boolean

true if a queue with the specified path exists; otherwise, false.

Exceptions

ArgumentException

The path syntax is not valid.

MessageQueueException

An error occurred when accessing a Message Queuing method.

-or-

The Exists(String) method is being called on a remote private queue

InvalidOperationException

The application used format name syntax when verifying queue existence.

Examples

The following code example verifies whether a Message Queuing queue exists, and then deletes it.

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

using namespace System;
using namespace System::Messaging;
int main()
{
   
   // Determine whether the queue exists.
   if ( MessageQueue::Exists( ".\\myQueue" ) )
   {
      try
      {
         
         // Delete the queue.
         MessageQueue::Delete( ".\\myQueue" );
      }
      catch ( MessageQueueException^ e ) 
      {
         if ( e->MessageQueueErrorCode == MessageQueueErrorCode::AccessDenied )
         {
            Console::WriteLine( "Access is denied. Queue might be a system queue." );
         }
         
         // Handle other sources of MessageQueueException.
      }

   }

   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 verifies existence and attempts to
        // delete a queue.
        //**************************************************

        public static void Main()
        {

            // Determine whether the queue exists.
            if (MessageQueue.Exists(".\\myQueue"))
            {
                try
                {
                    // Delete the queue.
                    MessageQueue.Delete(".\\myQueue");
                }
                catch(MessageQueueException e)
                {
                    if(e.MessageQueueErrorCode ==
                        MessageQueueErrorCode.AccessDenied)
                    {
                        Console.WriteLine("Access is denied. " +
                            "Queue might be a system queue.");
                    }

                    // Handle other sources of MessageQueueException.
                }
            }
        
            return;
        }
    }
}

Imports System.Messaging



Public Class MyNewQueue


        
        ' Provides an entry point into the application.
        '		 
        ' This example verifies existence and attempts to 
        ' delete a queue.
        

        Public Shared Sub Main()

            ' Determine whether the queue exists.
            If MessageQueue.Exists(".\myQueue") Then

                Try

                    ' Delete the queue.
                    MessageQueue.Delete(".\myQueue")

                Catch e As MessageQueueException

                    If e.MessageQueueErrorCode = _
                        MessageQueueErrorCode.AccessDenied Then

                        Console.WriteLine("Access is denied. " _
                            + "Queue might be a system queue.")
                    End If

                    ' Handle other sources of exceptions as necessary.

                End Try

            End If


            Return

        End Sub

End Class

Remarks

The Exists(String) method determines whether a Message Queuing queue exists at a specified path. No method exists to determine whether a queue with a specified format name exists. For more information about the format name syntax and other path syntax forms, see the Path property.)

Exists(String) is an expensive operation. Use it only when it is necessary within the application.

Note

The Exists(String) method does not support the FormatName prefix.

The syntax for the path parameter depends on the type of queue, as shown in the following table.

Queue type	Syntax
Public queue	MachineName\QueueName

Exists(String) cannot be called to verify the existence of a remote private queue.

For more syntax, see the Path property.

Alternatively, you can use the Label to describe the queue path.

Reference	Syntax
Label	Label:[ label ]

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	No
Remote computer	No
Remote computer and direct format name	No

See also

• Path