c# - Why there are 5 Versions of Timer Classes in .NET?

Question

Why are there five timer classes in the .Net framework, namely the following:

1. System.Timers.Timer
2. System.Threading.Timer
3. System.Windows.Forms.Timer
4. System.Web.UI.Timer
5. System.Windows.Threading.DispatcherTimer

Why are there several versions of the Timer class? And what are the differences between them?

Answer 1

Here's a description of the primary timers and the points that i find to be the most noteworthy.

Winforms.Timer

• ticks on UI thread not guaranteed to ticket at a specific time
• ticks delayed until UI thread is idle
• will skip ticks if the UI thread is busy

DispatcherTimer

• invoked on UI thread
• can set priority for what level of 'idle' is required to generate a tick
• will skip ticks

Threading.Timer

• ticks on a worker thread from threadpool - no option for specifying thread
• ticks are always fired on time
• none are skipped - you must guard against new ticks while you're still processing a former tick
• unhandled exceptions will crash the application

Timers.Timer

• wrapper around threading timer
• ticks on a worker thread taken from the CLR threadpool
• can force to tick on a specific thread by supplying a SynchronizationObject
• ticks are always fired on time
• none are skipped
• silently eats exceptions