Making a thread Foreground VS Thread.Join()

Question

If a foreground thread is a thread that prevents a process from terminating until all foreground threads belonging to the process have finished, and if the

Answer 1

The difference is the concept of Fire and Forget.i.e. One does not wait for the end of the thread. If one calls the Join method then you are explicitly waiting for the thread to finish execution.

Answer 2

The difference is that when a process shuts down/exits/stops it needs all its foreground threads to stop before it can safely terminate. Your second code although it gives the same result as the first one, it differs in the way it behaves. Join blocks the execution of the your main thread which is a foreground thread of that process making it impossible to safely terminate the process unless your background thread finishes execution.

The main benefit of foreground threads comes when you try starting threads from another background thread.

Say you are trying to write a thread that writes vital data to disk and that thread gets started from a background thread. Now you need to make sure that if the user decides to close your process, that the thread writing the data will not abnormally terminate mid way before completing its designated task.

Imagine you have such a scenario:

static void Main()
{
   Thread backgroundThread = new Thread(new ThreadStart(SomeMethod));
   thread.IsBackground = true;
   backgroundThread.Start();
} 


static void SomeMethod() 
{
   Thread thread = new Thread(new ThreadStart(SomeOtherMethod));
   thread.Name = "ForegroundThread";
   thread.IsBackground = false;
   thread.Start();
}

Here although your main thread creates a background thread without a wait or join, your process will never exit until the foreground thread created by the background thread exits.