private void btnnew_Click(object sender, EventArgs e)
        {
            FormChoice fch = new FormChoice();

            fch.ShowDialog();
            FormDataGridChoice_Load(null, null);
        }
        private void btnedit_Click(object sender, EventArgs e)
        {
            string ed = dgvchoice[0, dgvchoice.CurrentRow.Index].Value.ToString();
            Choice ch = new Choice();

            ch.cid = int.Parse(ed);
            DataTable  dt  = ch.selectone();
            FormChoice fch = new FormChoice();

            fch.txtcid.Text     = dt.Rows[0]["cid"].ToString();
            fch.txtfid.Text     = dt.Rows[0]["fid"].ToString();
            fch.txtnamel.Text   = dt.Rows[0]["cnamelessen"].ToString();
            fch.txtnamet.Text   = dt.Rows[0]["cnameteacher"].ToString();
            fch.txtdate.Text    = dt.Rows[0]["cdate"].ToString();
            fch.txtcid.ReadOnly = true;
            fch.btninsert.Text  = "ویرایش";
            fch.ShowDialog();
            FormDataGridChoice_Load(null, null);
        }