Question

I have a Form with a Label with text “Loading”.

label1.Text = "Loading...";

In Form.Load I have a new Thread which is doing something, lets say this.

void Form_Load(object sender, EventArgs args)
{
   Thread t = new Thread(run);
   t.Start();
}  

void run()
{
   for(int i = 0; i < 1000000; i++)
   {

   }
}

I want to change label1.Text property to “Finished” after the completion of Thread “t”. But where and how to change I don’t have any idea. I am learning Threads. Do I have to create one more thread to do this which continouously checks the isAlive property of Thread “t”?

Answer 1

You have multiple solution. If you really want to use the Thread class, you can call the Join method, but this will block the UI thread which is not a good thing. You could also call the Invoke method of your form right after your “for” loop as so

void run()
{
    for (int i = 0; i < 100000000; i++)
    {
    }

    this.Invoke(new Action(() => this.label1.Text = "done"));
}

The invoke method is required because you are in a windows form and the invoke method will execute your code on the UI thread.

Instead of using the Thread class, you could also have a look at Delegate.BeginInvoke and at System.Threading.Tasks. They are both more efficient since it pool the threads and the provide callback to separate your tear-down code.