I was trying to port an old app from c# 2.0 to WPF in 4.0. In one place I was using a Timer to handle filtering of a list from a text box. This kept the list from constantly being updated while the user is typing because it was getting data from the database. I set a 250 millisecond interval so whenever they paused it would update the list. The Timer class apparently got completely redefined in .Net 4.0. It used to have a Tick event, but this was changed to Ellapsed. Also I found out that it didn't ......