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This article will explain in detail how to solve the memory leak caused by the survival mechanism of C# timer. The content of the article is of high quality, so the editor shares it for you as a reference. I hope you will have a certain understanding of the relevant knowledge after reading this article.

There are three kinds of timers in C #. Timers in System.Windows.Forms work exactly the same way as System.Timers.Timer, so we will only discuss System.Timers.Timer and System.Threading.Timer here.

1. Timer keeps alive

Let's take a look at an example:

Class Program {static void Main (string [] args) {Start (); GC.Collect (); Read ();} static void Start () {Foo f = new Foo (); System.Threading.Thread.Sleep (5000000);}} public class Foo {System.Timers.Timer _ timer; public Foo () {_ timer = new System.Timers.Timer (1000); _ timer.Elapsed + = timer_Elapsed; _ timer.Start () } private void timer_Elapsed (object sender, System.Timers.ElapsedEventArgs e) {WriteLine ("System.Timers.Timer Elapsed.");} ~ Foo () {WriteLine ("- End -");}}

The running results are as follows:

System.Timers.Timer Elapsed.System.Timers.Timer Elapsed.System.Timers.Timer Elapsed.System.Timers.Timer Elapsed.System.Timers.Timer Elapsed.System.Timers.Timer Elapsed.System.Timers.Timer Elapsed....

After the end of the Start method, the Foo instance has lost its scope and is supposed to be reclaimed, but it is not (it is certain that the instance is not recycled because the destructor is not executed).

This is the preservation mechanism of the timer, because the timer needs to execute the timer_Elapsed method, which belongs to the Foo instance, so the Foo instance is saved.

But most of the time this is not what we want, and the result is a memory leak. The solution is to Dispose the timer first.

Public class Foo: IDisposable {... Public void Dispose () {_ timer.Dispose ();}}

A good rule is that if an object assigned to any field in a class implements the IDisposable interface, the class should also implement the IDisposable interface.

In this example, not only the Dispose method, but also the Stop method and setting AutoReset = false can serve the purpose of releasing the object. However, if the Start method is called after the Stop method, the object is still kept alive, and the object cannot be reclaimed even if it is forced garbage collection after the Stop.

The survival mechanism of System.Timers.Timer and System.Threading.Timer is similar.

The survival mechanism is because the timer refers to the method in the instance, so what if the timer does not refer to the method in the instance?

2. The difference between System.Timers.Timer and System.Threading.Timer under unguaranteed condition.

To eliminate the reference of the timer to the instance method is also very simple, just change the timer_Elapsed method to static. (static methods belong to classes, not instances. )

Run the example again after changing it to a static method, and the result is as follows:

System.Timers.Timer Elapsed.System.Timers.Timer Elapsed.System.Timers.Timer Elapsed.System.Timers.Timer Elapsed.- End-System.Timers.Timer Elapsed.System.Timers.Timer Elapsed.System.Timers.Timer Elapsed....

The Foo instance is destroyed (the destructor is running and the End is printed), but the timer is still executing. Why?

This is because. NET Framework ensures the survival of the System.Timers.Timer, even if the instance it belongs to has been destroyed and recycled.

What will happen if it is changed to System.Threading.Timer?

Class Program {static void Main (string [] args) {Start (); GC.Collect (); Read ();} static void Start () {Foo2 f2 = new Foo2 (); System.Threading.Thread.Sleep (5000000);}} public class Foo2 {System.Threading.Timer _ timer; public Foo2 () {_ timer = new System.Threading.Timer (timerTick, null, 0, 1000);} static void timerTick (object state) {WriteLine ("System.Threading.Timer Elapsed.") } ~ Foo2 () {WriteLine ("- End -");}}

Note that the timerTick method here is static. The running results are as follows:

System.Threading.Timer Elapsed.System.Threading.Timer Elapsed.System.Threading.Timer Elapsed.System.Threading.Timer Elapsed.System.Threading.Timer Elapsed.- End-

As you can see, with the destruction of the Foo2 instance, _ timer is automatically stopped and destroyed.

This is because,. NET Framework does not save the reference to the active System.Threading.Timer, but references the callback delegate directly.

On how to solve the memory leak caused by the C# timer survival mechanism is shared here, I hope the above content can be of some help to you, can learn more knowledge. If you think the article is good, you can share it for more people to see.

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