protected void lbDelete_Click(object sender, EventArgs e)
 {
     try
     {
         invObj       = new InvoiceClass();
         invObj.invId = Convert.ToInt32(((LinkButton)sender).CommandArgument);
         if (invObj.DeleteInvoiceByInvId())
         {
             BindAllInvoice();
             ScriptManager.RegisterStartupScript(this.Page, this.GetType(), "script", "successfull('Invoice Deleted Successfully.','')", true);
         }
         else
         {
             ScriptManager.RegisterStartupScript(this.Page, this.GetType(), "script", "failed('Failed to Delete Invoice.','')", true);
         }
     }
     catch (Exception ex)
     {
         ex.Message.ToString();
     }
 }