Will thread be disposed if an object sets to null

Question

I have a class ClassA

public class ClassA
{
    public ClassA()
    {
        Thread t = new Thread(EndlessLoop);
        t.IsBackground = True;
        t.Start();
    }

    private void EndlessLoop()
    {
        while (True)
        {
    // do something 
        }
    }
}

and I'm not sure if the thread will be disposed if I set ClassA object to null

ClassA a = new ClassA();

# will the thread exit ?
a = null;

Or maybe I should implement IDisposable, and call it manually?

I would add a bool variable shouldRun and set it to true. Implement IDisposable and in the dispose method set shouldRun to false so the EndlessLoop can exit. — Ken Tucker, Dec 06 '19 at 01:07

score 4 · Answer 1 · answered Dec 06 '19 at 01:09

Once started, the thread will terminate after the routine comes to an end (or Thread.Abort is invoked or the program exits). The Thread class doesn't implement IDisposable so there's no Dispose method to call. To terminate a long-running thread, you could set a flag that the thread checks periodically.

The Thread object is eligible to be garbage collected once it goes out of scope and is no longer referenced. However, the spawned thread will continue running.

score 4 · Answer 2 · answered Dec 06 '19 at 01:10

Nothing going to happen to the OS thread if you remove last refence to the Thread object corresponding to it - C# Thread object lifetime. The thread will continue to run the code until the method finishes (unlikely in while(true) case shown), thread is terminated with Abort (don't do that - What's wrong with using Thread.Abort()) or process ends.

The only good option is to somehow notify thread's code that it should finish (i.e. using events or even global variable protected by lock). Also consider if using Task and async with corresponding cancellation mechanism would simplify code (it would not solve infinite loop issue but give good framework to write cancellable operations).

Note that you can't "dispose" thread because it does not implement Dispose (Do we need to dispose or terminate a thread in C# after usage?),

Will thread be disposed if an object sets to null

2 Answers2