I have the following problem: I need to bind an asynchronous method to the Window.Closing event. Since the Closing event expects a CancelEventHandler with void signature, my WindowClosing method can’t be of type Task. So I have this:

public void Window_Closing(object sender, System.ComponentModel.CancelEventArgs e)
{
    DeinitializeThisFirst();
    DeinitializeThisAfterwards();
}

For hardware reasons, DeinitializeThisFirst() must finish before DeinitializeThisAfterwards() is called. But DeinitializeThisFirst() is an awaitable Task. Since I can’t change the signature of Window_Closing to be a Task, I can’t do this:

public async Task Window_Closing(object sender, System.ComponentModel.CancelEventArgs e)
{
    await DeinitializeThisFirst();
    DeinitializeThisAfterwards();
}

And since I am on the UI thread, this will cause a deadlock:

public void Window_Closing(object sender, System.ComponentModel.CancelEventArgs e)
{
    DeinitializeThisFirst().ConfigureAwait(false).GetAwaiter().GetResult();
    DeinitializeThisAfterwards();
}

Executing it in a separate Task will cause DeinitializeThisAfterwards() to be executed prematurely:

public void Window_Closing(object sender, System.ComponentModel.CancelEventArgs e)
{
    Task.Run(async () => await DeinitializeThisFirst());
    DeinitializeThisAfterwards();
}

And wrapping it in ContinueWith() will prevent both from being executed since the window is closed immediately:

public void Window_Closing(object sender, System.ComponentModel.CancelEventArgs e)
{
    DeinitializeThisFirst().ContinueWith(_ =>
    {
        DeinitializeThisAfterwards();
    });
}

I am at a loss here. Can anyone help?