Question

I’ve got thread, which processes some analytic work.

   private static void ThreadProc(object obj)
    {
        var grid = (DataGridView)obj;
        foreach (DataGridViewRow row in grid.Rows)
        {
            if (Parser.GetPreparationByClientNameForSynonims(row.Cells["Prep"].Value.ToString()) != null)
                UpdateGridSafe(grid,row.Index,1);
            Thread.Sleep(10);
        }
    }

I want safely update my gridView at loop, so I use classic way:

    private delegate void UpdateGridDelegate(DataGridView grid, int rowIdx, int type);
    public static void UpdateGridSafe(DataGridView grid, int rowIdx, int type)
    {
        if (grid.InvokeRequired)
        {
            grid.Invoke(new UpdateGridDelegate(UpdateGridSafe), new object[] { grid, rowIdx, type });
        }
        else
        {
            if (type == 1)
                grid.Rows[rowIdx].Cells["Prep"].Style.ForeColor = Color.Red;
            if (type==2)
                grid.Rows[rowIdx].Cells["Prep"].Style.ForeColor = Color.ForestGreen;

        }
    }

But when I enter UpdateGridSafe, the program hangs.

In the debugger, I see that grid.Invoke doesn’t invoke UpdateGridSafe. Please help – what’s wrong?

EDIT

Classic thread create code

        Thread t = new Thread(new ParameterizedThreadStart(ThreadProc));
        t.Start(dgvSource);
        t.Join();
        MessageBox.Show("Done", "Info");

Answer 1

You have a deadlock. Your t.Join is blocking the GUI thread until ThreadProc is done. ThreadProc is blocked waiting for t.Join to finish so it can do the Invokes.

Bad Code

    Thread t = new Thread(new ParameterizedThreadStart(ThreadProc)); 
    t.Start(dgvSource); 
    t.Join();  <--- DEADLOCK YOUR PROGRAM
    MessageBox.Show("Done", "Info"); 

Good Code

   backgroundWorker1.RunWorkerAsync

  private void backgroundWorker1_DoWork(object sender, 
        DoWorkEventArgs e)
    {    
        var grid = (DataGridView)obj;    
        foreach (DataGridViewRow row in grid.Rows)    
        {    
            if (Parser.GetPreparationByClientNameForSynonims(row.Cells["Prep"].Value.ToString()) != null)    
                UpdateGridSafe(grid,row.Index,1);    
            // don't need this Thread.Sleep(10);    
        }    
    }  

   private void backgroundWorker1_RunWorkerCompleted(
            object sender, RunWorkerCompletedEventArgs e)
        {
        MessageBox.Show("Done", "Info"); 
}

EDIT

Also use BeginInvoke instead of Invoke. That way your worker thread doesn’t have to block every time you update the GUI.

Reference

Avoid Invoke(), prefer BeginInvoke()