ControllerMove.cs

public static class FormExtensions
{
    public static void EnableDragging(this Control c)
    {
        // Long way, but strongly typed.        
        var downs =
            from down in Observable.FromEvent<MouseEventHandler, MouseEventArgs>(
                eh => new MouseEventHandler(eh),
                eh => c.MouseDown += eh,
                eh => c.MouseDown -= eh)
            select new { down.EventArgs.X, down.EventArgs.Y };

        // Short way.        
        var moves = from move in Observable.FromEvent<MouseEventArgs>(c, "MouseMove")
                    select new { move.EventArgs.X, move.EventArgs.Y };

        var ups = Observable.FromEvent<MouseEventArgs>(c, "MouseUp");

        var drags = from down in downs
                    from move in moves.TakeUntil(ups)
                    select new Point { X = move.X - down.X, Y = move.Y - down.Y };

        drags.Subscribe(drag => c.SetBounds(c.Location.X + drag.X, c.Location.Y + drag.Y, 0, 0, BoundsSpecified.Location));
    }
}