System.Timers.Timer vs System.Threading.Timer

Question

I have been checking out some of the possible timers lately, and System.Threading.Timer and System.Timers.Timer are the ones that look needful to me (since they support thre

Answer 1

This article offers a fairly comprehensive explanation:

"Comparing the Timer Classes in the .NET Framework Class Library" - also available as a .chm file

The specific difference appears to be that System.Timers.Timer is geared towards multithreaded applications and is therefore thread-safe via its SynchronizationObject property, whereas System.Threading.Timer is ironically not thread-safe out-of-the-box.

I don't believe that there is a difference between the two as it pertains to how small your intervals can be.

Answer 2

From MSDN: System.Threading.Timer is a simple, lightweight timer that uses callback methods and is served by thread pool threads. It is not recommended for use with Windows Forms, because its callbacks do not occur on the user interface thread. System.Windows.Forms.Timer is a better choice for use with Windows Forms. For server-based timer functionality, you might consider using System.Timers.Timer, which raises events and has additional features.

Source

Answer 3

The two classes are functionally equivalent, except that System.Timers.Timer has an option to invoke all its timer expiration callbacks through ISynchronizeInvoke by setting SynchronizingObject. Otherwise, both timers invoke expiration callbacks on thread pool threads.

When you drag a System.Timers.Timer onto a Windows Forms design surface, Visual Studio sets SynchronizingObject to the form object, which causes all expiration callbacks to be called on the UI thread.

Answer 4

Information from Microsoft about this (see Remarks on MSDN):

• System.Timers.Timer, which fires an event and executes the code in one or more event sinks 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, which 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 and executes the code in one or more event sinks at regular intervals. The component has no user interface and is designed for use in a single-threaded environment; it executes on the UI thread.
• System.Web.UI.Timer (.NET Framework only), an ASP.NET component that performs asynchronous or synchronous web page postbacks at a regular interval.

It is interesting to mention that System.Timers.Timer was deprecated with .NET Core 1.0, but was implemented again in .NET Core 2.0 (/ .NET Standard 2.0). The goal with .NET Standard 2.0 was that it should be as easy as possible to switch from the .NET Framework which is probably the reason it came back.

When it was deprecated, the .NET Portability Analyzer Visual Studio Add-In recommended to use System.Threading.Timer instead.

Looks like that Microsoft favors System.Threading.Timer before System.Timers.Timer.

EDIT NOTE 2018-11-15: I hand to change my answer since the old information about .NET Core 1.0 was not valid anymore.

Answer 5

I found a short comparison from MSDN

The .NET Framework Class Library includes four classes named Timer, each of which offers different functionality:

System.Timers.Timer, which fires an event and executes the code in one or more event sinks 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, which 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, a Windows Forms component that fires an event and executes the code in one or more event sinks at regular intervals. The component has no user interface and is designed for use in a single-threaded environment.

System.Web.UI.Timer, an ASP.NET component that performs asynchronous or synchronous web page postbacks at a regular interval.

Answer 6

One important difference not mentioned above which might catch you out is that System.Timers.Timer silently swallows exceptions, whereas System.Threading.Timer doesn't.

For example:

var timer = new System.Timers.Timer { AutoReset = false };
timer.Elapsed += (sender, args) =>
{
    var z = 0;
    var i = 1 / z;
};
timer.Start();

vs

var timer = new System.Threading.Timer(x =>
{
    var z = 0;
    var i = 1 / z;
}, null, 0, Timeout.Infinite);