Why use Windows.Forms.Timer at all?

问题:

I read this excellent article Comparing the Timer Classes in the .NET Framework Class Library and came to the conclusion that anything I could do with Windows.Forms.Timer I can do better with Timers.Timer - and then some.

So the obvious question that comes to mind is: Why is the Windows.Forms Timer offered at all?

Legacy (backward compatibility) support?

Other?

回答1:

The main convenience of the Windows.Forms.Timer is that its events are fired on the UI (Winforms) thread. If your timer events perform UI operations, it may be the simplest alternative (instead of calling Control.Invoke/BeginInvoke or SynchronizationContext.Post/Send inside all of your events).

回答2:

The Windows.Forms.Timer events get invoked on the UI thread so you can update the UI from the event handlers directly, which is not normally the case with Timers.Timer (as you would get cross thread access violation exceptions).

And, as @Robert Harvey answered, it also has designer support.

回答3:

One of advantage of Windows.Forms is that it run in the same thread of GUI and you do not get cross thread exceptions while accessing Form controls.

回答4:

Windows.Forms.Timer has designer support. So it behaves like any other Winforms component (i.e. you can drag it onto a form, it's part of the Controls collection, etc).

Timer events raised by System.Windows.Forms.Timer class are synchronous with respect to the rest of the code in your Windows Forms app. This means that application code that is executing will never be preempted by an instance of this timer class (assuming you don't call Application.DoEvents). Events fired by the Windows.Forms.Timer class are compatible with your Winform controls; you can safely interact with them without having to call Invoke().

The System.Timers.Timer class is a server-based timer that was designed and optimized for use in multithreaded environments. Instances of this timer class can be safely accessed from multiple threads. Although Invoke() is technically required to interact with Winforms, the Timer class does provide a SynchronizingObject property, to which you can attach the Windows form with which you want to safely interact.

More here: http://msdn.microsoft.com/en-us/magazine/cc164015.aspx

回答5:

Well I think the answer is that they are two completely different types of timers. The Windows.Forms.Timer is a single-threaded application timer that's well suited for timers existing on the client running application.

A Timer is used to raise an event at user-defined intervals. This Windows timer is designed for a single-threaded environment where UI threads are used to perform processing. It requires that the user code have a UI message pump available and always operate from the same thread, or marshal the call onto another thread.

In contrast the Timers.Timer is a server-based timer that is better suited for Windows services.

The Timer component is a server-based timer, which allows you to specify a recurring interval at which the Elapsed event is raised in your application. You can then handle this event to provide regular processing. For example, suppose you have a critical server that must be kept running 24 hours a day, 7 days a week. You could create a service that uses a Timer to periodically check the server and ensure that the system is up and running. If the system is not responding, the service could attempt to restart the server or notify an administrator.

You can find their documentation and read the excerpts and more from Microsoft.

It's not that one should never be used or always used, the serve two different purposes.

回答6:

My belief is that it is for winform designer integration, in that you can drag it onto a form, click it and set its properties in the properties pane.