如何在 .NET 中非同步等待進程退出而不阻塞 GUI？

/// <summary>
/// Waits asynchronously for the process to exit.
/// </summary>
/// <param name="process">The process to wait for cancellation.</param>
/// <param name="cancellationToken">A cancellation token. If invoked, the task will return immediately as canceled.</param>
/// <returns>A Task representing waiting for the process to end.</returns>
public static Task WaitForExitAsync(this Process process, 
CancellationToken cancellationToken = default(CancellationToken))
{
    if (process.HasExited) return Task.CompletedTask;

    var tcs = new TaskCompletionSource<object>();
    process.EnableRaisingEvents = true;
    process.Exited += (sender, args) => tcs.TrySetResult(null);
    if(cancellationToken != default(CancellationToken))
        cancellationToken.Register(() => tcs.SetCanceled());

    return process.HasExited ? Task.CompletedTask : tcs.Task;
}

public async void Test() 
{
   var process = new Process("processName");
   process.Start();
   await process.WaitForExitAsync();

   //Do some fun stuff here...
}