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MessageQueue.Exists Method

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

[Visual Basic]
Public Shared Function Exists( _
   ByVal path As String _
) As Boolean
[C#]
public static bool Exists(
 string path
);
[C++]
public: static bool Exists(
 String* path
);
[JScript]
public static function Exists(
   path : String
) : Boolean;

Parameters

path
The location of the queue to find.

Return Value

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

Exceptions

Exception Type Condition
ArgumentException The path syntax is invalid.
MessageQueueException An error occurred when accessing a Message Queuing API.

-or-

The Exists method is being called on a remote private queue

InvalidOperationException The application used a format name syntax when verifying queue existence.

Remarks

The Exists 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 is an expensive operation. Use it only when it is necessary within the application.

The syntax for the path parameter depends on the type of queue.

Queue Type Syntax
Public queue MachineName\ QueueName
Note    Exists 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 + direct format name No
Remote computer No
Remote computer + direct format name No

Example

[Visual Basic, C#, C++] The following example verifies whether a Message Queuing queue exists, and then deletes it.

[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 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 'Main

    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 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;
        }

    }
}

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

using namespace System;
using namespace System::Messaging;

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

    }

    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

MessageQueue Class | MessageQueue Members | System.Messaging Namespace | Create | Delete | Path

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