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MessageQueue.GetPublicQueuesByCategory Method

Retrieves all the public queues on the network that belong to the specified category.

[Visual Basic]
Public Shared Function GetPublicQueuesByCategory( _
   ByVal category As Guid _
) As MessageQueue()
[C#]
public static MessageQueue[] GetPublicQueuesByCategory(
 Guid category
);
[C++]
public: static MessageQueue* GetPublicQueuesByCategory(
 Guid category
) [];
[JScript]
public static function GetPublicQueuesByCategory(
   category : Guid
) : MessageQueue[];

Parameters

category
A Guid that groups the set of queues to be retrieved.

Return Value

An array of MessageQueue objects that reference the retrieved public queues.

Exceptions

Exception Type Condition
MessageQueueException An error occurred when accessing a Message Queuing API.

Remarks

Use this method to filter the public queues by category. The Category property provides access to the Message Queuing type ID property (which is read/write) of a particular queue. Although you can use NewGuid to create a category value that is unique across all Guid values, it is not necessary. The category value needs to be distinct only from other categories, not from all other Guid values. For example, you can assign {00000000-0000-0000-0000-000000000001} as the Category for one set of queues and {00000000-0000-0000-0000-000000000002} as the Category for another set.

GetPublicQueuesByCategory retrieves a static snapshot of the queues. To interact with a dynamic list of the queues, use GetMessageQueueEnumerator. You can specify the category as part of the MessageQueueCriteria you pass into the method.

The following table shows whether this method is available in various Workgroup modes.

Workgroup Mode Available
Local computer No
Local computer + direct format name No
Remote computer No
Remote computer + direct format name No

Example

[Visual Basic, C#, C++] The following example retrieves lists of queues.

[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 gets lists of queues by a variety
        ' of criteria.
        '**************************************************

        Public Shared Sub Main()

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

            ' Send normal and high priority messages.
            myNewQueue.GetQueuesByCategory()
            myNewQueue.GetQueuesByLabel()
            myNewQueue.GetQueuesByComputer()
            myNewQueue.GetAllPublicQueues()
            myNewQueue.GetPublicQueuesByCriteria()
            myNewQueue.GetPrivateQueues()

            Return

        End Sub 'Main


        '**************************************************
        ' Gets a list of queues with a specified category.
        ' Sends a broadcast message to all queues in that
        ' category.
        '**************************************************

        Public Sub GetQueuesByCategory()

            ' Get a list of queues with the specified category.
            Dim QueueList As MessageQueue() = _
                MessageQueue.GetPublicQueuesByCategory(New _
                Guid("{00000000-0000-0000-0000-000000000001}"))

            ' Send a broadcast message to each queue in the array.
            Dim queueItem As MessageQueue
            For Each queueItem In QueueList
                queueItem.Send("Broadcast message.")
            Next queueItem

            Return

        End Sub 'GetQueuesByCategory


        '**************************************************
        ' Gets a list of queues with a specified label.
        ' Sends a broadcast message to all queues with that
        ' label.
        '**************************************************

        Public Sub GetQueuesByLabel()

            ' Get a list of queues with the specified label.
            Dim QueueList As MessageQueue() = _
                MessageQueue.GetPublicQueuesByLabel("My Label")

            ' Send a broadcast message to each queue in the array.
            Dim queueItem As MessageQueue
            For Each queueItem In QueueList
                queueItem.Send("Broadcast message.")
            Next queueItem

            Return

        End Sub 'GetQueuesByLabel


        '**************************************************
        ' Gets a list of queues on a specified computer. 
        ' Displays the list on screen.
        '**************************************************

        Public Sub GetQueuesByComputer()

            ' Get a list of queues on the specified computer.
            Dim QueueList As MessageQueue() = _
                MessageQueue.GetPublicQueuesByMachine("MyComputer")

            ' Display the paths of the queues in the list.
            Dim queueItem As MessageQueue
            For Each queueItem In QueueList
                Console.WriteLine(queueItem.Path)
            Next queueItem

            Return

        End Sub 'GetQueuesByComputer


        '**************************************************
        ' Gets a list of all public queues.
        '**************************************************        

        Public Sub GetAllPublicQueues()

            ' Get a list of public queues.
            Dim QueueList As MessageQueue() = _
                MessageQueue.GetPublicQueues()

            Return

        End Sub 'GetAllPublicQueues


        '**************************************************
        ' Gets a list of all public queues that match 
        ' specified criteria. Displays the list on 
        ' screen.
        '**************************************************

        Public Sub GetPublicQueuesByCriteria()

            ' Define criteria to filter the queues.
            Dim myCriteria As New MessageQueueCriteria()
            myCriteria.CreatedAfter = DateTime.Now.Subtract(New _
                TimeSpan(1, 0, 0, 0))
            myCriteria.ModifiedBefore = DateTime.Now
            myCriteria.MachineName = "."
            myCriteria.Label = "My Queue"

            ' Get a list of queues with that criteria.
            Dim QueueList As MessageQueue() = _
                MessageQueue.GetPublicQueues(myCriteria)

            ' Display the paths of the queues in the list.
            Dim queueItem As MessageQueue
            For Each queueItem In QueueList
                Console.WriteLine(queueItem.Path)
            Next queueItem

            Return

        End Sub 'GetPublicQueuesByCriteria


        '**************************************************
        ' Gets a list of private queues on the local 
        ' computer. Displays the list on screen.
        '**************************************************

        Public Sub GetPrivateQueues()

            ' Get a list of queues with the specified category.
            Dim QueueList As MessageQueue() = _
                MessageQueue.GetPrivateQueuesByMachine(".")

            ' Display the paths of the queues in the list.
            Dim queueItem As MessageQueue
            For Each queueItem In QueueList
                Console.WriteLine(queueItem.Path)
            Next queueItem

            Return

        End Sub 'GetPrivateQueues

    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 gets lists of queues by a variety
        // of criteria.
        //**************************************************

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

            // Send normal and high priority messages.
            myNewQueue.GetQueuesByCategory();
            myNewQueue.GetQueuesByLabel();
            myNewQueue.GetQueuesByComputer();
            myNewQueue.GetAllPublicQueues();
            myNewQueue.GetPublicQueuesByCriteria();
            myNewQueue.GetPrivateQueues();
                        
            return;
        }


        //**************************************************
        // Gets a list of queues with a specified category.
        // Sends a broadcast message to all queues in that
        // category.
        //**************************************************
        
        public void GetQueuesByCategory()
        {
            // Get a list of queues with the specified category.
            MessageQueue[] QueueList = 
                MessageQueue.GetPublicQueuesByCategory(new 
                Guid("{00000000-0000-0000-0000-000000000001}"));

            // Send a broadcast message to each queue in the array.
            foreach(MessageQueue queueItem in QueueList)
            {
                queueItem.Send("Broadcast message.");
            }
            
            return;
        }


        //**************************************************
        // Gets a list of queues with a specified label.
        // Sends a broadcast message to all queues with that
        // label.
        //**************************************************
        
        public void GetQueuesByLabel()
        {
            // Get a list of queues with the specified label.
            MessageQueue[] QueueList = 
                MessageQueue.GetPublicQueuesByLabel("My Label");

            // Send a broadcast message to each queue in the array.
            foreach(MessageQueue queueItem in QueueList)
            {
                queueItem.Send("Broadcast message.");
            }
            
            return;
        }


        //**************************************************
        // Gets a list of queues on a specified computer. 
        // Displays the list on screen.
        //**************************************************
        
        public void GetQueuesByComputer()
        {
            // Get a list of queues on the specified computer.
            MessageQueue[] QueueList = 
                MessageQueue.GetPublicQueuesByMachine("MyComputer");

            // Display the paths of the queues in the list.
            foreach(MessageQueue queueItem in QueueList)
            {
                Console.WriteLine(queueItem.Path);
            }

            return;
        }


        //**************************************************
        // Gets a list of all public queues.
        //**************************************************
        
        public void GetAllPublicQueues()
        {
            // Get a list of public queues.
            MessageQueue[] QueueList = 
                MessageQueue.GetPublicQueues();
    
            return;
        }


        //**************************************************
        // Gets a list of all public queues that match 
        // specified criteria. Displays the list on 
        // screen.
        //**************************************************
        
        public void GetPublicQueuesByCriteria()
        {
            // Define criteria to filter the queues.
            MessageQueueCriteria myCriteria = new 
                MessageQueueCriteria();
            myCriteria.CreatedAfter = DateTime.Now.Subtract(new 
                TimeSpan(1,0,0,0));
            myCriteria.ModifiedBefore = DateTime.Now;
            myCriteria.MachineName = ".";
            myCriteria.Label = "My Queue";
            
            // Get a list of queues with that criteria.
            MessageQueue[] QueueList = 
                MessageQueue.GetPublicQueues(myCriteria);

            // Display the paths of the queues in the list.
            foreach(MessageQueue queueItem in QueueList)
            {
                Console.WriteLine(queueItem.Path);
            }

            return;
        }


        //**************************************************
        // Gets a list of private queues on the local 
        // computer. Displays the list on screen.
        //**************************************************
        
        public void GetPrivateQueues()
        {
            // Get a list of queues with the specified category.
            MessageQueue[] QueueList = 
                MessageQueue.GetPrivateQueuesByMachine(".");

            // Display the paths of the queues in the list.
            foreach(MessageQueue queueItem in QueueList)
            {
                Console.WriteLine(queueItem.Path);
            }
            
            return;
        }
    }
}

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

using namespace System;
using namespace System::Messaging;
using namespace System::Collections;

__gc class MyNewQueue 
{
    // Gets a list of queues with a specified category.
    // Sends a broadcast message to all queues in that
    // category.
public:
    void GetQueuesByCategory() 
    {
        // Get a list of queues with the specified category.
        MessageQueue* QueueList[] = 
            MessageQueue::GetPublicQueuesByCategory( 
            Guid(S" {00000000-0000-0000-0000-000000000001}"));

        // Send a broadcast message to each queue in the array.
        IEnumerator* myEnum = QueueList->GetEnumerator();
        while (myEnum->MoveNext()) 
        {
            MessageQueue* queueItem = __try_cast<MessageQueue*>(myEnum->Current);
            queueItem->Send(S"Broadcast message.");
        }
        return;
    }

    // Gets a list of queues with a specified label.
    // Sends a broadcast message to all queues with that
    // label.
public:
    void GetQueuesByLabel() 
    {
        // Get a list of queues with the specified label.
        MessageQueue* QueueList[] = 
            MessageQueue::GetPublicQueuesByLabel(S"My Label");

        // Send a broadcast message to each queue in the array.
        IEnumerator* myEnum = QueueList->GetEnumerator();
        while (myEnum->MoveNext()) 
        {
            MessageQueue* queueItem = __try_cast<MessageQueue*>(myEnum->Current);

            queueItem->Send(S"Broadcast message.");
        }

        return;
    }

    // Gets a list of queues on a specified computer. 
    // Displays the list on screen.
public:
    void GetQueuesByComputer() 
    {
        // Get a list of queues on the specified computer.
        MessageQueue* QueueList[] = 
            MessageQueue::GetPublicQueuesByMachine(S"MyComputer");

        // Display the paths of the queues in the list.
        IEnumerator* myEnum = QueueList->GetEnumerator();
        while (myEnum->MoveNext()) 
        {
            MessageQueue* queueItem = __try_cast<MessageQueue*>(myEnum->Current);

            Console::WriteLine(queueItem->Path);
        }

        return;
    }

    // Gets a list of all public queues.
public:
    void GetAllPublicQueues() 
    {
        // Get a list of public queues.
        MessageQueue* QueueList[] = MessageQueue::GetPublicQueues();

        return;
    }


    // Gets a list of all public queues that match 
    // specified criteria. Displays the list on 
    // screen.
public:
    void GetPublicQueuesByCriteria() 
    {
        // Define criteria to filter the queues.
        MessageQueueCriteria* myCriteria = new MessageQueueCriteria();
        myCriteria->CreatedAfter = DateTime::Now.Subtract(TimeSpan(1, 0, 0, 0));
        myCriteria->ModifiedBefore = DateTime::Now;
        myCriteria->MachineName = S".";
        myCriteria->Label = S"My Queue";

        // Get a list of queues with that criteria.
        MessageQueue* QueueList[] = 
            MessageQueue::GetPublicQueues(myCriteria);

        // Display the paths of the queues in the list.
        IEnumerator* myEnum = QueueList->GetEnumerator();
        while (myEnum->MoveNext()) 
        {
            MessageQueue* queueItem = __try_cast<MessageQueue*>(myEnum->Current);

            Console::WriteLine(queueItem->Path);
        }

        return;
    }

    // Gets a list of private queues on the local 
    // computer. Displays the list on screen.
public:
    void GetPrivateQueues() 
    {
        // Get a list of queues with the specified category.
        MessageQueue* QueueList[] = 
            MessageQueue::GetPrivateQueuesByMachine(S".");

        // Display the paths of the queues in the list.
        IEnumerator* myEnum = QueueList->GetEnumerator();
        while (myEnum->MoveNext()) 
        {
            MessageQueue* queueItem = __try_cast<MessageQueue*>(myEnum->Current);

            Console::WriteLine(queueItem->Path);
        }

        return;
    }
};

// Provides an entry point into the application.
// This example gets lists of queues by a variety
// of criteria.
int main() 
{
    // Create a new instance of the class.
    MyNewQueue* myNewQueue = new MyNewQueue();

    // Send normal and high priority messages.
    myNewQueue->GetQueuesByCategory();
    myNewQueue->GetQueuesByLabel();
    myNewQueue->GetQueuesByComputer();
    myNewQueue->GetAllPublicQueues();
    myNewQueue->GetPublicQueuesByCriteria();
    myNewQueue->GetPrivateQueues();

    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 | Category | GetPublicQueues | GetPublicQueuesByLabel | GetPublicQueuesByMachine | GetMessageQueueEnumerator | GetPrivateQueuesByMachine

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