Comparison of Timer Class in .Net Class Library

	System.Windows.Forms	System.Timers	System.Threading
Timer event runs on what thread?	UI thread	UI or worker thread	Worker thread
Instances are thread safe?	No	Yes	No
Familiar/intuitive object model?	Yes	Yes	No
Requires Windows Forms?	Yes	No	No
Metronome-quality beat?	No	Yes*	Yes*
Timer event supports state object?	No	No	Yes
Initial timer event can be scheduled?	No	No	Yes
Class supports inheritance?	Yes	Yes	No
* Depending on the availability of system resources (for example, worker threads)

For details descrition : http://msdn.microsoft.com/en-us/magazine/cc164015.aspx