C# WPF Timer.,......

Have a look at the DispatcherTimer[^] class in WPF.

WPF is the abbreviated "Windows Presentation Foundation". You cannot "add" a timer for a foundation.
Timers already exist you should only use them. There are three types of timers: System.Threading.Timer and System.Timers.Timer are quite suitable for use with WPF, but System.Windows.Forms.Timer is not. Frankly, the last one is not very good even for use with Forms, it's just very well simplified. Don't try to use it and you will be fine. Use first two types instead.

See:
http://msdn.microsoft.com/en-us/library/system.threading.timer.aspx[^],
http://msdn.microsoft.com/en-us/library/system.timers.timer.aspx[^].

[EDIT]
Completely forgot about System.Windows.Threading.DispatcherTimer, Abhinav reminded us about.
[END EDIT]

Note that I don't believe you really need a timer. In most cases it's much better to use a thread, possible calling System.Threading.Thread.Sleep. This approach is usually a good replacement of using the timer; it's more robust and gives you much less trouble.

—SA

You can also add "standard" timer. But, you have to add little trick at it's Elapsed event handler:

private void OnTimedEvent(object source, ElapsedEventArgs e)
{
    Dispatcher.Invoke(new Action(()=>
         {
              ANY ACTIONS HERE
         }), null);
}

You have to call Invoke method, because Dispatcher handles flow in main thread in WPF.