How to Kill a Thread Instantly in C#

How to kill a thread instantly in C#?

The reason it's hard to just kill a thread is because the language designers want to avoid the following problem: your thread takes a lock, and then you kill it before it can release it. Now anyone who needs that lock will get stuck.

What you have to do is use some global variable to tell the thread to stop. You have to manually, in your thread code, check that global variable and return if you see it indicates you should stop.

How to kill a thread in C# effectively?

Set an Abort flag to tell the thread is needs to terminate. Append a dummy record to the ServiceBroker queue. The WAITFOR then returns. The thread then checks its 'Abort' flag and, finding it set, deletes the dummy record from the queue and exits.

Another variant would be to add a 'real' poison-pill record to the specification for the table monitored by the ServiceBroker - an illegal record-number, or the like. That would avoid touching the thread/s at all in any direct manner - always a good thing:) This might be more complex, especially if each work thread is expeceted to notify upon actual termination, but would still be effective if the work threads, ServiceBroker and DB were all on different boxes. I added this as an edit because, having thought a bit more about it, it seems more flexible, after all, if the threads normally only communicate via. the DB, why not shut them down with only the DB? No Abort(), no Interrupt() and, hopefully, no lockup-generating Join().

How to kill Thread in C# instantly

Don't do a ReadToEnd, instead create a loop and read X chars at a time (or read a line at a time with ReadLine). Within the loop check whether an AutoResetEvent is set (using .WaitOne(0)), if it is then exit the loop.

Set the reset event (using Set) in your other thread when you want to stop the download.

Terminating a thread immediately and safely (C#)

This sort of thing can be implemented easier and cleaner using async/await rather than threads.

First we need to wrap the blocking console input method with one that is cancellable (and async). The method polls the console using KeyAvailable and asynchronously delaying while checking the CancellationToken.

    public static async Task<ConsoleKeyInfo> ReadKeyAsync(CancellationToken cancellationToken)
    {
        while (!Console.KeyAvailable)
        {
            await Task.Delay(100, cancellationToken);
        }
        return Console.ReadKey();
    }

Now we can start this async method and pass a cancellation token from a CancellationTokenSource that will automatically cancel after a specific amount of time (10 seconds as an example).

    public static async Task Main(string[] args)
    {
        Console.WriteLine("You have 10 seconds to press the Y key...");
        var cts = new CancellationTokenSource(10_000);
        try
        {
            while (true)
            {
                var key = await ReadKeyAsync(cts.Token);
                if (key.Key == ConsoleKey.Y)
                {
                    Console.WriteLine("Good job!");
                    break;
                }
                else
                {
                    Console.WriteLine("Wrong Key");
                }
            }
        }
        catch (OperationCanceledException)
        {
            Console.Write("Time up!");
        }
    }

c# Stop Thread with a button click

SampleFunction is a method, not a Thread object, so you can't call Abort() like that.

You need to keep a reference to the Thread:

var thread = new Thread(SampleFunction);
thread.Start();

Then you can call Abort() when you want to kill it:

thread.Abort();

But keep in mind that it does kill it. The effect of Abort() is that it throws a ThreadAbortException in the thread. So it can stop at any moment and leave things in an unexpected state, so it may not be the best approach depending on what you're doing in the thread.

Here are a couple articles that discuss this and possibly better ways to stop a thread:

• Destroying threads
• Canceling threads cooperatively

How to immediately kill a thread which is waiting for network operations?

You could Dispose the ResponseStream and then catch an ObjectDisposedException.

While this may work i suggest you design your application using CancellationToken to allow it to gracefully close instead of abruptedly aborting threads. You also might consider using async-await to make your application more scalable and non-blocking.

How to terminate a thread in C#?

Thread.Abort will "kill" the thread, but this is roughly equivalent to:

Scenario: You want to turn off your computer

Solution: You strap dynamite to your computer, light it, and run.

It's FAR better to trigger an "exit condition", either via CancellationTokenSource.Cancel, setting some (safely accessed) "is running" bool, etc., and calling Thread.Join. This is more like:

Scenario: You want to turn off your computer

Solution: You click start, shut down, and wait until the computer powers down.

Best way to terminate a thread

In general you have two options:

• allow the thread to terminate itself. This covers your first option.

• terminate the thread externally. This covers your other options.

And that's it. And none of them, in general, can prevent the threads from running for indefinite time after they should (from the programmer's intent point of view) terminate.

The most predictable approach is the first one. If terminating takes too long, try to do the processing in smaller steps to allow checking the termination flag more frequently. Also, note the IsBackground flag which will help with the application being unable to close itself.

The whole problem with the other options is that any code (except for some special cases like finally blocks) can be just interrupted in the middle of its execution, which can lead to some undesired results (e.g. some unmanaged resources not released) - as it is explained in Thread.Abort documentation.

Note that the third approach in the newest versions of .NET framework is equivalent to calling the Abort method on your executing threads, as explained in the documentation:

The threads in domain are terminated using the Abort method, which throws a ThreadAbortException in the thread. Although the thread should terminate promptly, it can continue executing for an unpredictable amount of time in a finally clause.

So it seems better to use Thread.Abort from these two, as it's simpler and more readable.

If the first approach is problematic, and if you are well aware of the type of operations your thread is executing and there is no problem in interrupting them in-between then the "brutal" approach should be fine.

Stop C# thread immediately without Thread.Abort()

You could use the Thread.Interrupt method. This API is supported in the current .NET platform.

Interrupts a thread that is in the WaitSleepJoin thread state.

If this thread is not currently blocked in a wait, sleep, or join state, it will be interrupted when it next begins to block.

ThreadInterruptedException is thrown in the interrupted thread, but not until the thread blocks. If the thread never blocks, the exception is never thrown, and thus the thread might complete without ever being interrupted.

You'll have to handle a possible ThreadInterruptedException inside the body of the ThreadStart delegate, otherwise the process may crash when the Interrupt is invoked. Or you could just handle all exceptions with a generic catch (Exception) handler, as you are currently doing.

---

Related Topics