Question

I’m just trying to run a new thread each time a button click even occurs which should create a new form. I tried this in the button click event in the MainForm:

private void button1_Click(object sender, EventArgs e)
{
    worker1 = new Thread(new ThreadStart(thread1));
    worker2 = new Thread(new ThreadStart(thread2));

    worker1.Start();
    worker2.Start();
}

private void thread1()
{
    SubForm s = new SubForm();
    s.Show();
}

private void thread2()
{
    SubForm s = new SubForm();
    s.Show();
}

The code in the Subform button click event goes like this:

private void button1_Click(object sender, EventArgs e)
{
    int max;
    try
    {
        max = Convert.ToInt32(textBox1.Text);
    }
    catch
    {
        MessageBox.Show("Enter numbers", "ERROR");
        return;
    }

    progressBar1.Maximum = max;

    for ( long i = 0; i < max; i++)
    {
        progressBar1.Value = Convert.ToInt32(i);
    }          
}

Is this the right way? Because I’m trying to open two independent forms, operations in one thread should not affect the other thread.

Or is BackGroundworker the solution to implement this? If yes, can anyone please help me with that?

Answer 1

Although I’m not 100% aware of anything that says running completely seperate forms doing completely isolated operations in their own threads is dangerous in any way, running all UI operations on a single thread is generally regarded as good practice.

You can support this simply by having your Subform class use BackgroundWorker. When the form is shown, kick off the BackgroundWorker so that it processes whatever you need it to.

Then you can simply create new instances of your Subform on your GUI thread and show them. The form will show and start its operation on another thread.

This way the UI will be running on the GUI thread, but the operations the forms are running will be running on ThreadPool threads.

Update

Here’s an example of what your background worker handlers might look like – note that (as usual) this is just off the top of my head, but I think you can get your head around the basic principles.

Add a BackgroundWorker to your form named worker. Hook it up to the following event handlers:

void worker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
    // Executed on GUI thread.
    if (e.Error != null)
    {
        // Background thread errored - report it in a messagebox.
        MessageBox.Show(e.Error.ToString());
        return;
    }

    // Worker succeeded.
}

void worker_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
    // Executed on GUI thread.
    progressBar1.Value = e.ProgressPercentage;
}

void worker_DoWork(object sender, DoWorkEventArgs e)
{
    // Executed on ThreadPool thread.
    int max = (int)e.Argument;

    for (long i = 0; i < max; i++)
    {
        worker.ReportProgress(Convert.ToInt32(i));
    }
}

Your click handler would look something like:

void button1_Click(object sender, EventArgs e)
{
    int max;

    try
    {
        // This is what you have in your click handler,
        // Int32.TryParse is a much better alternative.
        max = Convert.ToInt32(textBox1.Text);
    }
    catch
    {
        MessageBox.Show("Enter numbers", "ERROR");
        return;
    }

    progressBar1.Maximum = max;

    worker.RunWorkerAsync(max);
}

I hope that helps.