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

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?

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

Timers.Timer generates an event after a set interval, with an option to generate recurring events. MSDN

Windows.Forms.Timer is a Control for winforms.

Web.UI.Timer performs asynchronous or synchronous Web page postbacks at a defined interval. MSDN

Threading.Timer is the timer for Callbacks. Creates a new Thread for working. Served by thread pool threads. MSDN

So, these timers have different purposes, also they are served by different tools.

This question is now answered by Microsoft in the MSDN article for system.timers.timer

https://docs.microsoft.com/en-us/dotnet/api/system.timers.timer?view=net-5.0

> Tip > > Be aware that .NET includes four classes named Timer, each of which > offers different functionality:

> System.Timers.Timer (this topic): fires an event at regular intervals. The class is intended for use as a server-based or service > component in a multithreaded environment; it has no user interface and > is not visible at runtime.

> System.Threading.Timer: executes a single callback method on a thread pool thread at regular intervals. The callback method is > defined when the timer is instantiated and cannot be changed. Like the > System.Timers.Timer class, this class is intended for use as a > server-based or service component in a multithreaded environment; it > has no user interface and is not visible at runtime.

> System.Windows.Forms.Timer (.NET Framework only): a Windows Forms component that fires an event at regular intervals. The component has > no user interface and is designed for use in a single-threaded > environment.

> System.Web.UI.Timer (.NET Framework only): an ASP.NET component that performs asynchronous or synchronous web page postbacks at a > regular interval.