如何在 c# 中使用异步？

Question

I am doing c # form application. The application is basically a video converter implementation. I have two buttons called convert and conver the stop. Here's what I want to do; I don't want the form to lock itself, even if I click on any of these. I may cancel the process or close the form at that time. I need to do async, but I don't know how. I can't use a backgroundworker because I'm basically dealing with big data. He can lock the form more. Please help.

convert the stop code;

private void Button7_Click(object sender, EventArgs e)
    {
        var ffmpeg = new NReco.VideoConverter.FFMpegConverter();
        ffmpeg.Stop();
                MessageBox.Show("convert is stopped");
    }

Answer 1

Like this:

private async void Button7_Click(object sender, EventArgs e)
{
    await Task.Run(() => 
    {
        //code here that takes a long time. NB nothing that must be run on the main thread
        var ffmpeg = new NReco.VideoConverter.FFMpegConverter();
        ffmpeg.Stop();
    });
    //when the above task completes this will then be called on the original thread context (i.e. the main ui thread)
    MessageBox.Show("convert is stopped");
}

Note that the MessageBox.Show will be called after the task has completed but the control will return to the main thread at the await call. This is what confuses people new to async.

Also note that ordinarily an async function will have a Task or Task<T> return type, but as this is an event handler it has void return type. It is one of the few cases where a void return type is correct for an async function.