Azure Service Bus WinForms App - Not Receiving/Displaying Messages-CodePudding

I am trying to display messages to a list box in a WinForms application but it is not working. I am using the most recent Azure namespace, hence using asynchronous methods. Below is Program.cs:

namespace App
{
    public class Program
    {
    static ServiceBusClient client;
    static ServiceBusProcessor processor;
    public static List<string> data = new List<string>();
            [STAThread]
            public static async Task MessageHandler(ProcessMessageEventArgs args)
            {
    
                string body = args.Message.Body.ToString();
                 data.Add(body);
                // complete the message. messages is deleted from the subscription. 
                await args.CompleteMessageAsync(args.Message);
            }
            public static void Main(string[] args)
            {
                Application.Run(new Form1());
            }
            public static async Task MainAsync()
            {
                
                client = new ServiceBusClient(_serviceBusConn);
                // create a processor that we can use to process the messages
                processor = client.CreateProcessor(_serviceBustopic, _ServiceBusSubscription, new ServiceBusProcessorOptions());
            try
            {
                // add handler to process messages
                processor.ProcessMessageAsync  = MessageHandler;
                // add handler to process any errors
                processor.ProcessErrorAsync  = ErrorHandler;
                // start processing 
                   await processor.StartProcessingAsync();
                
            }
            finally
            {

                await processor.DisposeAsync();
                await client.DisposeAsync();
            }
       } 
    }
}
//end of Program.cs

And the Form.cs:

namespace App
{
    public partial class Form1 : Form
    {
        public static List<string> AppNames = new List<string>();
        public Form1()
        {
            InitializeComponent();
            
        }
        public static async Task receiveMessage()
        {
            await Program.MainAsync();
            AppNames = Program.data;
        }
        public async void button1_Click(object sender, EventArgs e)
        {
            await receiveMessage();
            for (int i = 0; i < AppNames.Count; i  )
            {
                listBox1.Items.Add("item"   AppNames[i].ToString());
            }
            
        }
    }
}

There is a console version of this program that is functional, but I cannot seem to get it to display the messages in this Winforms Application. Some debugging showed me that the program was getting into the Main async. method upon the button being clicked, but it was not going into the Message Handler despite messages being sent through the service bus.

CodePudding user response：

The pattern that you're using for the Service Bus client and processor isn't going to work in your scenario.

In MainAsync, when you call StartProcessingAsync, the method will return once the processor has started. Execution is then going to reach the finally block, where the processor and client are disposed. At that point, the processor is not running and, therefore, is not receiving messages.

Each time button1_Click runs, you're creating a new set of clients, establishing a new connection to Azure, and then immediately throwing them away.

The processor is intended to be a long-lived type that runs continuously in the background, calling back into your code as messages are available. Likewise, the client is intended to be used as a singleton for the lifetime of your application. I'd suggest reading through the Service Bus "Hello World" sample, which would help to explain some of the types and recommended patterns for use.