Manage queues by using the C# SDK

Before you begin

Before you begin, ensure that you have:

• An Alibaba Cloud account or RAM user with the required permissions

• An AccessKey pair (AccessKey ID and AccessKey secret). To create one, go to the AccessKey Management page or the RAM console

• The regional SMQ endpoint for your queue. Endpoints vary by region. To find your endpoint, go to the SMQ console and click View the endpoints of a queue. For more information, see View the endpoints of a queue

Set up the SDK

1. Download the latest version of the SDK for C# and decompress the package.

2. Add the decompressed folder to Visual Studio as a solution. The solution contains four projects.

3. Right-click the AliyunSDK_MNS project and select Rebuild. This generates the Aliyun.MNS.dll file in the bin directory.

   Note

   Add a reference to Aliyun.MNS.dll in any project that calls the SMQ SDK.

4. Open the SyncTopicSample.cs file in the AliyunSDK_MNS_Sample project.

5. Set the following properties in Visual Studio:

   • Set AliyunSDK_MNS_Sample as the startup project.

   • Set SyncTopicSample as the startup object.

6. At the top of SyncTopicSample.cs, specify your AccessKey ID, AccessKey secret, and endpoint.

Create a queue

Create a queue with custom parameters. The default queue name in the sample code is myqueue.

// Configure queue parameters. For a full list, see Queue in the API reference.
var createQueueRequest = new CreateQueueRequest
{
    QueueName = _queueName,
    Attributes =
    {
        VisibilityTimeout = 30,          // Seconds a received message stays invisible. Default: 30.
        MaximumMessageSize = 40960,      // Maximum message size in bytes.
        MessageRetentionPeriod = 345600, // Seconds a message is retained. Default: 345600 (4 days).
        PollingWaitSeconds = 30          // Long polling timeout in seconds. Maximum: 30.
    }
};

try
{
    var queue = client.CreateQueue(createQueueRequest);
    Console.WriteLine("Create queue successfully, queue name: {0}", queue.QueueName);
}
catch (MNSException me)
{
    // Common causes: network error, queue name already exists.
    Console.WriteLine("CreateQueue Failed! ErrorCode: " + me.ErrorCode);
}
catch (Exception ex)
{
    Console.WriteLine("Create queue failed, exception info: " + ex.Message);
}

To create a queue with default parameters, call client.CreateQueue(_queueName) directly.

Send a message

After the queue is created, send a message to it:

try
{
    // Get a reference to the queue.
    var nativeQueue = client.GetNativeQueue(_queueName);

    // Build a send request with a message body.
    var sendMessageRequest = new SendMessageRequest("Alibaba<MessageBody>Cloud");

    // Send the message.
    var sendMessageResponse = nativeQueue.SendMessage(sendMessageRequest);
    Console.WriteLine("Send message succeed");
}
catch (MNSException me)
{
    Console.WriteLine("SendMessage Failed! ErrorCode: " + me.ErrorCode);
}
catch (Exception ex)
{
    Console.WriteLine("Send message failed, exception info: " + ex.Message);
}

To send a plain-text message without extra parameters, call nativeQueue.SendMessage("MessageBody").

Receive and delete a message

try
{
    // Long poll for up to 30 seconds.
    var receiveMessageResponse = nativeQueue.ReceiveMessage(30);

    // Save the receipt handle for later deletion.
    // The receipt handle is valid for the duration of VisibilityTimeout.
    _receiptHandle = message.ReceiptHandle;
}
catch (MNSException me)
{
    Console.WriteLine("ReceiveMessage Failed! ErrorCode: " + me.ErrorCode);
}
catch (Exception ex)
{
    Console.WriteLine("ReceiveMessage failed, exception info: " + ex.Message);
}

try
{
    var deleteMessageResponse = nativeQueue.DeleteMessage(_receiptHandle);
}
catch (MNSException me)
{
    // A MessageNotExist error means the receipt handle has expired.
    // To avoid this, set VisibilityTimeout to a value that gives your
    // application enough time to process the message, or call
    // changeMessageVisibility() to extend it.
    Console.WriteLine("DeleteMessage Failed! ErrorCode: " + me.ErrorCode);
}
catch (Exception ex)
{
    Console.WriteLine("Delete message failed, exception info: " + ex.Message);
}

Delete a queue

When a queue is no longer needed, delete it to release resources:

try
{
    var deleteQueueResponse = client.DeleteQueue(deleteQueueRequest);
}
catch (MNSException me)
{
    Console.WriteLine("DeleteQueue Failed! ErrorCode: " + me.ErrorCode);
}
catch (Exception ex)
{
    Console.WriteLine("Delete queue failed, exception info: " + ex.Message);
}