private void frm_PurchaseForm_Load(object sender, EventArgs e)
 {
     cmb_Category.DataSource   = _a.FillCategory();
     cmb_PayMode.SelectedIndex = 0;
     if (BillType == "Update")
     {
         pnl_OldPay.Visible = true;
         Date           = Convert.ToDateTime(CustomerBill.Rows[0]["Date"].ToString());
         dtp_Date.Value = Date;
     }
     else
     {
         dt_cust = _Cust.GetCustomerDeatils();
         this.BringToFront();
         cmb_Name.DataSource        = dt_cust;
         cmb_SalesPerson.DataSource = _common.GetSalesPerson();
         cmb_Name.Select();
         Clear();
         Masterclear();
     }
 }