Object not released without reference to the timer

Question

0.00/5 (No votes)

See more:

public class Program
    {
        
        public static void Main(string[] args)
        {
            object obj = new ObjectWithTimer();
            Console.ReadLine();
            Console.WriteLine("obj=null");
            obj = null;
            Console.ReadLine();
        }
    }

    public class ObjectWithTimer
    {
        private int i;
        public System.Timers.Timer t;
        public ObjectWithTimer()
        {
            t = new System.Timers.Timer(5000);
            t.Elapsed += Obj_Elapsed;
            t.Enabled = true;
        }

        public void Obj_Elapsed(object sender, ElapsedEventArgs e)
        {
            i++;
            Console.WriteLine(i);
        }
    }

What I have tried:

Hi all, 
Please see example below. Even though the reference to obj is set to null, the obj is not released and Obj_Elapsed continues printing i. Notice there is no reference to the timer out of the scope of the ObjectWithTimer constructor.

Posted 11-Feb-20 10:02am

Member 14741901

Updated 13-Feb-20 23:55pm

Add a Solution

2 solutions

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

OriginalGriff · Answer 1 · 2020-02-11T10:33:00

Variables aren't the same thing as the instance they contain: just setting a variable to null doesn't change the object it used to "point to", and it doesn't in any way mean that the system will immediately destroy (or even begin the process of destroying) the object itself.

Think of it in terms of cars: you own a car. You put your mobile in the glove box and sell the car. The new owner drives off into the sunset in his new car.
Where is your mobile?

You sold the car: you set the "pointer" "my car" to null - but that doesn't change the car itself in any way! It still drives, it still needs fuel, it still has your mobile in the glove box. Just you can't access the car, it's glove box, or your mobile any more because you discarded the only reference you had to it.

When you set up a timer it runs until all references to it are gone, and the system gets so low on memory that the Garbage Collector is kicked into action to decide what to dispose.
You want to stop the timer? Do just that:

C#

Console.WriteLine("obj=null");
obj.t.Enabled = false;
obj = null;
Console.ReadLine();

George Swan · Answer 2 · 2020-02-13T23:56:00

If your class uses an object that implements IDisposable, as the Timer does, you should implement IDisposable in your class. You can then place your class within the confines of a using statement so that Dispose gets called when it goes out of scope and when an exception is thrown. Also, you will not be allowed to reassign the class instance within a using block and your error will be flagged up by the compiler.

C#

static async Task Main()
       {

           {
               using ObjectWithTimer owt = new ObjectWithTimer();
               Console.ReadLine();
           }
           Console.WriteLine("Exited using's scope. Timer disposed.");
           Console.ReadLine();
       }
public sealed  class ObjectWithTimer : IDisposable
   {
       private int i;
       public Timer timer;
       public ObjectWithTimer()
       {
           timer = new Timer(2000);
           timer.Elapsed += TimerElapsed;
           timer.Enabled = true;
       }

       public void TimerElapsed(object sender, ElapsedEventArgs e)
       {
           i++;
           Console.WriteLine(i);
       }

       public void Dispose()
       {

           timer.Dispose();

       }
   }

Object not released without reference to the timer

2 solutions

Solution 1

Solution 2

Add your solution here

Preview 0