//Fields
        private Button currentButton;
        private Random Random;
        private int tempIndex;
        private Form ActiveForm1; 
//
private void OpenChildForm(Form childForm, object btnSender)
        {
            if(ActiveForm1!= null)
            {
                ActiveForm1.Close();
            }
            ActivateButton(btnSender);
            ActiveForm1 = childForm;
            childForm.TopLevel = false;
            childForm.FormBorderStyle = FormBorderStyle.None;
            childForm.Dock = DockStyle.Fill;
            this.Workspace_panel.Controls.Add(childForm);
            this.Workspace_panel.Tag = childForm;
            childForm.BringToFront();
            childForm.Show();
            
            Lable_title.Text = childForm.Text;
            
            
            

        }
        private void button3_Click(object sender, EventArgs e)
        {
            OpenChildForm(new Forms.Form_Cai_dat(), sender);
           
        }

      
        private void button1_Click(object sender, EventArgs e)
        {
            OpenChildForm( new Forms.FormLine1(),sender);

        }

        private void button2_Click(object sender, EventArgs e)
        {
            OpenChildForm(new Forms.FormLine2(), sender);
        }

        private void button4_Click(object sender, EventArgs e)
        {
            OpenChildForm(new Forms.Form_Trich_xuat_file(), sender);
        }
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