Calling asynchronous function synchronously is more responsive-CodePudding

I have an asynchronous method like this:

private async Task TaskAsync()
{
    await Task.Run(() => Task.Delay(2000));
}

I then call it in a button-click event, which I've declared like this:

private async void button1_Click(object sender, EventArgs e)
{
    await TaskAsync();

    MessageBox.Show("Afterwards.");
}

Now, when I click on the button, TaskAsync() is literally awaited on, and the message box isn't shown until TaskAsync() has finished executing. However, when I remove the await command when calling TaskAsync() in the click event, then execution immediately jumps to the message box.

Am I doing something wrong here? Is this normal behavior of async...await?

My project is a .NET Core 5 C# winform project.

CodePudding user response：

There are two problems here. First, the TaskAsync method is using Task.Run to run another async method. That just wastes a thread. It should be just :

private async Task TaskAsync()
{
    await Task.Delay(2000);
}

if not

private Task TaskAsync()=>Task.Delay(2000);

Second, if a Task isn't awaited execution will proceed immediately. That's the whole point of using await - awaiting an already executing asynchronous task to complete without blocking the calling thread.

The original code is equivalent to :

private async void button1_Click(object sender, EventArgs e)
{
    await Task.Delay(2000);

    MessageBox.Show("Afterwards.");
}

Without await, the task returned by Task.Delay() will be ignored and the message box will be displayed immediately.