panel = new Panel();
            panel.BorderStyle = BorderStyle.FixedSingle;
            panel.AutoScroll = true;
            panel.Dock = DockStyle.Fill;
            panel.GotFocus += Control1_GotFocus;   //<_________________
            tab_page3.GotFocus += Control2_GotFocus;  //<------------
          //  panel.Invalidate();

            tab_page1.Controls.Add(table);
            tab_page2.Controls.Add(data);
            tab_page3.Controls.Add(panel);

            tab_menu.Controls.AddRange(new Control[] { tab_page1, tab_page2, tab_page3 });
            Controls.Add(tab_menu);

            Open_file(file, nRows);
            Data_to_paint();

            tab_menu.Visible = false;          
            Paint += Modul_Paint;
            tab_menu.Visible = true;  
            Invalidate();
        }
        private void Control1_GotFocus(Object sender, EventArgs e) {

           l.WriteLine("You are in the Panel.GotFocus event.");

        }
        private void Control2_GotFocus(Object sender, EventArgs e) {

           l.WriteLine("You are in the TabPanel3.GotFocus event.");

        }
        void Modul_Paint(object sender, PaintEventArgs e)
        {
            Graphics g = panel.CreateGraphics();
            g.DrawLines(new Pen(Color.Black), point_paint.ToArray());
           l.WriteLine("You are in paint event.");

        }

            tab_menu.Controls.Add( tab_page3);
            tab_menu.Controls.Add( tab_page2);
            tab_menu.Controls.Add( tab_page1);
            tab_menu.SelectedIndexChanged  ///[color=red] <-----------------------------------------!!![/color]
               += new System.EventHandler(this.tabControl1_SelectedIndexChanged);

            Controls.Add(tab_menu);
            

            Open_file(file, nRows);
            Data_to_paint();

            tab_menu.Visible = false;          
            Paint += Modul_Paint;
            tab_menu.Visible = true;  
            Modul_Paint(this, new PaintEventArgs (CreateGraphics() ,ClientRectangle));
            this.Load += new System.EventHandler(this.Form1_Load);
          //  Invalidate();
        }

        private void tabControl1_SelectedIndexChanged(object sender, EventArgs e)
        {
//            if (tab_menu.SelectedIndex == 0)
            if (tab_menu.SelectedIndex == 2)
            {
                l.WriteLine("SelectedIndexChanged index:{0}", tab_menu.SelectedIndex);
               // Invalidate();
           //    
             Modul_Paint(this, new PaintEventArgs (CreateGraphics() ,ClientRectangle));
            }
        }

        private void Form1_Load(object sender, EventArgs e)
        {
           Invalidate();
           Modul_Paint(this, new PaintEventArgs (CreateGraphics() ,ClientRectangle));
           l.WriteLine("You are in the Form1_Load event add Invalidate.");
        }


        private void Control1_GotFocus(Object sender, EventArgs e) {

           l.WriteLine("You are in the Panel.GotFocus event.");

        }

 
           panel.Paint += Modul_Paint;  // ПРАВИЛЬНО
         //   Paint += Modul_Paint;          //  НЕ ПРАВИЛЬНО
            tab_page3.Controls.Add(panel);        //график