How to stop threads?

Question

Hi guys I start threads with such code:

    Thread[] thr;
    private void button1_Click(object sender, EventArgs e)
    {
        decimal value = numericUpDown2         


        

Answer 1

A number of the answers say to abort the thread. Never abort a thread unless it is an emergency situation and you are shutting down the application.

The CLR guarantees that its internal data structures are not corrupted by a thread abort. This is the only (*) guarantee made by the CLR with respect to thread aborts. It specifically does not guarantee:

• That the thread actually will abort. Threads can harden themselves against being terminated.
• That any data structure that is not in the CLR itself will be uncorrupted. Thread aborts in the middle of crucial operations can leave BCL data structures or user data structures in arbitrarily inconsistent states. This can crash your process mysteriously later.
• That locks will be released. Aborting threads can cause locks to be held forever, it can cause deadlocks, and so on.

In case I am not being clear: it is insanely dangerous to abort a thread and you should only do so when all the alternatives are worse.

So what if you want to start up a thread and then shut it down cleanly?

First, don't do that. Don't start a thread in the first place. Start a Task with a cancellation token and when you want to shut it down, signal its cancellation token.

If you do have to start a thread, then start the thread such that there is some mechanism whereby the main thread and the working thread can cleanly and safely communicate "I want you to shut yourself down cleanly at this time".

If you don't know how to do that then stop writing multithreaded code until you learn how to do that.

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(*) This is a small lie; the CLR also makes certain guarantees with respect to the interactions of thread aborts and special code regions such as constrained execution regions and finally blocks.