Left mouse button click detect on winform using Reactive extensions IObservable on events

Just started reading on Reactive extensions. I am trying to watch a simple left mouse button click on my winform. Meaning anywhere there is a click (on any control on the form including the form) I just want to display a message "Click detected". So far I have

var mouseDown = Observable.FromEvent<MouseButtonEventArgs>(frmMain, "MouseDown");
//missing code please fill here 
mouseDown.Subscribe(() => Debug.WriteLine("left click detected.");

I know the first line will detect any mouse event. I want just the left mouse button click. Please post working code so I can understand this better. Right now in a tailspin with buzzwords I have never used before like .takeuntil etc.. Further refining my question. What 开发者_开发技巧is the Rx equivalent of

protected override void WndProc(ref Message m)
{
    Console.Writeline("{0}", m.Msg);
}

That should observe every observable mouse or keyboard event. thank you

---

Sorry, I'm not sure if thats working code (can't try it now) but it should get you started.

var mouseDown = Observable.FromEvent<MouseButtonEventArgs>(frmMain, "MouseDown")
                      .Where(x => x.LeftButton == MouseButtonState.Pressed);

mouseDown.Subscribe(() => Debug.WriteLine("left click detected.");