multithreading - Is there a good method in C# for throwing an exception on a given thread

Question

The code that I want to write is like this:

void MethodOnThreadA()
{
    for (;;)
    {
        // Do stuff
        if (ErrorConditionMet)
            ThrowOnThread(threadB, new MyException(...));
    }
}

void MethodOnThreadB()
{
    try
    {
        for (;;)
        {
            // Do stuff
        }
    }
    catch (MyException ex)
    {
        // Do the right thing for this exception.
    }
}

I know I can have thread B periodically check, in thread safe way, to see if a flag has been set by thread A, but that makes the code more complicated. Is there a better mechanism that I can use?

Here is a more fleshed out example of periodically checking:

Dictionary<Thread, Exception> exceptionDictionary = new Dictionary<Thread, Exception>();

void ThrowOnThread(Thread thread, Exception ex)
{
    // the exception passed in is going to be handed off to another thread,
    // so it needs to be thread safe.
    lock (exceptionDictionary)
    {
        exceptionDictionary[thread] = ex;
    }
}

void ExceptionCheck()
{
    lock (exceptionDictionary)
    {
        Exception ex;
        if (exceptionDictionary.TryGetValue(Thread.CurrentThread, out ex))
            throw ex;
    }
}

void MethodOnThreadA()
{
    for (;;)
    {
        // Do stuff
        if (ErrorConditionMet)
            ThrowOnThread(threadB, new MyException(...));
    }
}

void MethodOnThreadB()
{
    try
    {
        for (;;)
        {
            // Do stuff
            ExceptionCheck();
        }
    }
    catch (MyException ex)
    {
        // Do the right thing for this exception.
    }
}

Answer 1

There are enough problems with exceptions that can be thrown on threads by other mechanisms, like aborting threads and the likes, that you should find another way of doing it.

An exception is a mechanism used to signal that a process has experienced something exceptional that it cannot deal with. You should try to avoid writing the code so that an exception is used to signal that something else has experienced something exceptional.

That other thread will most likely not know how to handle the exception in all cases where it could be thrown by your code.

In short, you should find some other mechanism for aborting your threads than using exceptions.

Use event objects or similar to tell a thread to abort its processing, that's the best way.