public int?ValidateInvoiceOldByPay(int customerid, DateTime invoiceDateToValidate)
{
using (var db = new KoontabiDBEntities())
{
var result = db.Sp_ValidateInvoiceOldByPay(invoiceDateToValidate, customerid).FirstOrDefault();
return(result != null?result.InvoiceNumber:0);
}
}