Question

I made a form that plays a progressbar role here’s the code i made

  public partial class PXProgressBar : Form
    {
        public delegate bool CancelEvent();
        public event CancelEvent cancel_e;

        public Boolean ProcessCancelled
        {
            get;
            set;
        }
        public PXProgressBar(bool EnableCancel) 
        {
            InitializeComponent();
            ProcessCancelled = false;
            progressBar1.Minimum = 0;
            if (!EnableCancel)
                Cancelbtn.Visible = false;

        }
        public  void increament(int step)
        {
            if (progressBar1.Value < progressBar1.Maximum-1)
            {
                progressBar1.Value++;
                progressBar1.Caption = progressBar1.Value.ToString() + " of " + progressBar1.Maximum;
                progressBar1.Refresh();

            }

            else
            {
                progressBar1.Value++;
                progressBar1.Caption = progressBar1.Value.ToString() + " of " + progressBar1.Maximum;
                if (this.TopMost)
                    this.TopMost = false;
                this.Update();
                this.Hide();
                this.WindowState = FormWindowState.Minimized;
               // this.Dispose();
            }

        }
        public void SetMaximum(int MaximumValue)
        {
            if (MaximumValue <= 0)
            {
                progressBar1.Maximum = 0;
                return;
            }
            if (progressBar1.Minimum != 0 && MaximumValue < progressBar1.Minimum)
            {
                progressBar1.Maximum = progressBar1.Minimum;
                return;
            }
            progressBar1.Maximum = MaximumValue;


        }
        public void SetMinimum(int MinimumValue)
        {
            progressBar1.Value = 0;
            if (MinimumValue <= 0)
            {

                progressBar1.Minimum = 0;
                return;
            }
            if (progressBar1.Maximum != 100 && MinimumValue > progressBar1.Maximum)
            {
                progressBar1.Minimum = progressBar1.Maximum;
                return;
            }
            progressBar1.Minimum= MinimumValue;
        }
        public void SetTitle(string ProcessTitle)
        {
            this.ProgressTitlelb.Text =ProcessTitle;// ProcessTitle;
            //this.ProgressTitlelb.Left = (this.panel1.Width - this.ProgressTitlelb.Width) / 2;
            //this.ProgressTitlelb.Top = (this.panel1.Height - this.ProgressTitlelb.Height) / 2;
            this.Update();
        }

        private void Cancelbtn_Click(object sender, EventArgs e)
        {

            ProcessCancelled = true;
            bool disposeRequired =cancel_e();
            if(disposeRequired)
             this.Dispose();
        }

        private void PXProgressBar_Shown(object sender, EventArgs e)
        {
            this.Update();
        }

    }

and i call the form through this code

  if (ProgressBar == null)
   ProgressBar = new PXProgressBar(true);
   ProgressBar.SetTitle("Saving ...");
   ProgressBar.SetMinimum(0);
   ProgressBar.SetMaximum(100);
   ProgressBar.TopMost = true;
   ProgressBar.Show();
   Application.DoEvents();

regarding that the past few lines are in a unction that is called throught a thread
but when i run it the form hangs so i cant set a Cancel Button in the form to let the user cancel the operation

Answer 1

You need to make sure the GUI elements are created on the main form thread and not from a separate thread. So, you need to get you thread that is doing the work to get the main form thread to display and update the progress bar. This is going to take a bit of refactoring.

So, in your worker thread:

void DoWork () // of whatever it's called
{
  main_form.CreateProgressBar ();
  while (doing stuff)
  {
    main_form.IncrementProgressBar ();
    do stuff
  }
  main_form.DestroyProgressBar ();
}

And in the main form:

delegate void Callback ();

void CreateProgressBar ()
{
   if (InvokeRequired)
   {
     Invoke (new Callback (CreateProgressBar));
   }
   else
   {
     progress_bar = CreateProgressBar ();
   }
 }

void IncrementProgressBar ()
{
   if (InvokeRequired)
   {
     Invoke (new Callback (IncrementProgressBar ));
   }
   else
   {
     progress_bar.IncrementProgressBar ();
   }
 }

void DestroyProgressBar ()
{
   if (InvokeRequired)
   {
     Invoke (new Callback (DestroyProgressBar));
   }
   else
   {
     progress_bar.Close ();
     progress_bar = null;
   }
 }

The InvokeRequired determines if the calling thread is the same as the GUI thread. If the calling thread is not the GUI thread, the Invoke is used to changed thread context. This is the synchronous version and won’t complete until the invoked method is finished. There is an asynchronous version called BeginInvoke but this isn’t really needed for what your doing.