Running C++ code asynchronously in a C# program

Question

I wrote some backend code in C++ and I wrote a frontend for it in C#. What I want it to do is run the backend code in the background so I can do other things like update a progress bar, but when I click the "Start" button, the program hangs until it's finished running the backend code.

C# code:

    [DllImport("backend.dll", CallingConvention = CallingConvention.Cdecl)]
    public static extern int executeBackend();

    private async void startButton_Click(object sender, EventArgs e)
    {
        startButton.Enabled = false;
        await StartProgram();
    }

    private async Task StartProgram()
    {
        int status = 0;
        status = executeBackend(); //This is causing the UI to deadlock
        startButton.Enabled = true;
    }

backend.dll C++ code:

extern "C" {
    __declspec(dllexport) int executeBackend()
    {
        int statusCode = 0;
        //Do stuff in the background
        return statusCode;
    }
}

If I comment out the call to run executeBackend and replace it with await Task.Delay(5000);, the UI doesn't deadlock. How would I fix this?

Answer 1

You can wrap the call to executeBackend in a Task to prevent the UI from locking up.

var status = await Task.Run(() => executeBacked());

I also think you're confused about what the async keyword actually does. I think it might be prudent for you to read up on how Asynchronous Programming works in dotnet.