private void dataGridView1_RowHeaderMouseClick(object sender, DataGridViewCellMouseEventArgs e)
        {
            try
            {
                DataGridViewRow dr = dataGridView1.SelectedRows[0];
                if (string.IsNullOrEmpty(dr.Cells[0].Value.ToString()))
                {
                    return;
                }

                frmSubjectEntry frm = new frmSubjectEntry();
                // or simply use column name instead of index
                //dr.Cells["id"].Value.ToString();
                frm.Show();
                frm.txtSubjectCode.Text = dr.Cells[1].Value.ToString();
                frm.txtSubjectName.Text = dr.Cells[2].Value.ToString();
                frm.cmbClass.Text       = dr.Cells[3].Value.ToString();
                // frm.txtClassID.Text = dr.Cells[3].Value.ToString();
                frm.adding = false;
                frm.txtSubjectCode.Enabled = true;
                frm.Delete.Enabled         = true;
                frm.Update_record.Enabled  = true;
                frm.btnSave.Enabled        = false;
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
        }
        private void btnAddNew_Click(object sender, EventArgs e)
        {
            frmSubjectEntry frm = new frmSubjectEntry();

            frm.Show();
        }