Button Click event handler and using async void

Question

I am getting myself confused about async void and button handlers. I heard in a video tutorial that it was not wise to use async void. I have reviewed these questions:

In many answers it does actually use this syntax. Thus my confusion.

Here is my handler:

async private void InstallStyleButton_Clicked(object sender, EventArgs e)
{
    var customFileType =
        new FilePickerFileType(new Dictionary<DevicePlatform, IEnumerable<string>>
        {
            {DevicePlatform.macOS, new[] {"xsl"} }
        });

    var pickResult = await FilePicker.PickAsync(new PickOptions
    {
        FileTypes = customFileType,
        PickerTitle = "Select template to install"

    });

    if(pickResult != null)
    {
        // Build target path
        string targetFile = Path.Combine("/Users/Shared/VisitsRota.MacOS/Styles", pickResult.FileName);

        // OK to install?
        if(!File.Exists(targetFile)) 
        {
            // Install
            File.Copy(pickResult.FullPath, targetFile);

            // Add it
            StylesPicker.ItemsSource.Add(pickResult.FileName);

            // Select it
            StylesPicker.SelectedItem = pickResult.FileName;
        }
    }
}

I realise it is not a good idea to hardcode the folder path and I will eventually get around to that. Other than that, my handler appears to operate fine on my development MacBook Pro when I try it.

Is my use of async void with the button handler ok? And if not, how should my handler be adjusted?

score 0 · Answer 1 · answered Feb 13 '21 at 12:29

I found this link where it states:

To summarize this first guideline, you should prefer async Task to async void. Async Task methods enable easier error-handling, composability and testability. The exception to this guideline is asynchronous event handlers, which must return void.

So my code is OK.

Button Click event handler and using async void

1 Answers1