C#: Stopping a thread after an Exception

Question

I have this code:

Thread t = new Thread(() => UpdateImage(origin));
t.Name = "UpdateImageThread";
t.Start();

If method UpdateImage(origin) throw an exception, it is necessary to stop thread or it will be stoped after the exception?

Thank you!

Answer 1

If UpdateImage throws an exception, it is probably going to take down your whole process. Any thread that raises a top-level exception indicates a big problem. You should wrap this, for example by putting try/catch around UpdateImage and doing something suitable. And yes, if an exception gets to the top of a thread, the thread is dead:

Thread t = new Thread(() => {
    try {UpdateImage(origin); }
    catch (Exception ex) {Trace.WriteLine(ex);}
});
t.Name = "UpdateImageThread";
t.Start();

(or your choice of error handling)

Answer 2

Since .NET 2.0, when a background thread throws an exception (that is not handled), the .NET runtime will take down your process. In a Windows.Forms application, this is different; you can use the Application.ThreadException event to catch the exception.

This was different in .NET 1.0/1.1, you can read about the whole topic here (e.g. how to enable the legacy behavior with .NET 2.0 or later): http://msdn.microsoft.com/en-us/library/ms228965.aspx#ChangeFromPreviousVersions.

No matter whether you use Windows.Forms or the legacy behavior - if the process does not exit, you do not need to explicitly stop the thread; the exception will stop it.