Question

in my Winform a read file method is implemented on button click.when big files are read my Ui hangs until the loop is over.I need to have control on my UI all the time.

i know that is done before and i tried some but i am still having an
error when i try to use some form controls like this :(translated!)

the access of control element comboBox1 is from another thread rather than the thread in which it is created in !!!

   private void button1_Click(object sender, EventArgs e)

         {  
            //some code
            using (StreamReader sr = new StreamReader(file,  System.Text.Encoding.ASCII))
                 {

                   while (sr.EndOfStream == false)
                   {
                    line = sr.ReadLine();
                    UpdateProgressBar(line.Length);
                   }

                 }

              //some code
          }

Answer 1

Add a BackgroundWorker to your class on Form (or Control) load. Then hookup its events:

BackgroundWorker _worker;
void Form_Load(object sender, EventArgs e)
{
    _worker = new BackgroundWorker();
    _worker.DoWork += _worker_DoWork;
    _worker.RunWorkerCompleted += _worker_RunWorkerCompleted;
    _worker.ProgressChanged +=_worker_ProgressChanged;
    _worker.WorkerReportsProgress = true;
}

private void button1_Click(object sender, EventArgs e)
{
    _worker.RunWorkerAsync(file);//pass on the file name
}

private void _worker_DoWork(object sender, DoWorkEventArgs e)
{
    var file = e.Argument as String;
    using (StreamReader sr = new StreamReader(file, Encoding.ASCII))
    {
        while (sr.EndOfStream == false)
        {
            line = sr.ReadLine();
            _worker.ReportProgress(line.Length);
        }
    }
}

private void _worker_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
    //Report porogress bar change
    UpdateProgressBar(e.ProgressPercentage);
}

private void _worker_RunWorkerCompleted(object sender, 
                                   RunWorkerCompletedEventArgs e)
{
    //do any stuff you want after reading the file.
}

Read more about this here.