Question

Suppose I have a routine like this:

private void button1_Click(object sender, EventArgs e)
{
    Thread t = new Thread(new ThreadStart(Some_Work));
    t.Start();
}

I need to put a condition so that, “If there is not already a thread running apart from the Main thread, start a new thread”.

But how to test for whether a thread is running other than the Main thread?

Answer 1

The easiest solution is of course to either store a reference to the existing thread, or just set a flag that you have a thread running.

You should also maintain that field (reference or flag) so that if the thread exits, it should unset that field so that the next “start request” starts a new one.

Easiest solution:

private volatile Thread _Thread;

...

if (_Thread == null)
{
    _Thread = new Thread(new ThreadStart(Some_Work));
    _Thread.Start();
}

private void Some_Work()
{
    try
    {
        // your thread code here
    }
    finally
    {
        _Thread = null;
    }
}