C#

delegate void _delegate();

private void button1_Click(object sender, EventArgs e)
{
    Thread t1 = new Thread(new ThreadStart(ProgressUpdate));
    t1.Start();
}

void ProgressUpdate()
{
    if (progressBar1.InvokeRequired)
    {
        progressBar1.Invoke(new _delegate(Progress));
    }

    else
    {
        for (int i = 1; i <= 100; i++)
        {
            progressBar1.Value = (i * 100) / 100;
            Thread.Sleep(50);
        }
    }
}

void Progress()
{
    for (int i = 1; i <= 100; i++)
    {
        progressBar1.Value = i;
        Thread.Sleep(50);
    }
}