Count A field in table sql server by linq C#

 public List<Vw_Card_DepositDetail> GetCardDepositDetails(int receiptId, int? status, int pageIndex, int pageSize, out int total, out decimal totalAmount)  
     {  
       using(var db = _connectionFactory.Open())  
       {  
         var query = db.From<Vw_Card_DepositDetail>();  
         query.Where(x => x.ReceiptId == receiptId);  
         if(status != null) query.Where(x => x.Status == status);  
         total = Convert.ToInt32(db.Count(query));  
         //query.OrderByDescending(x => x.CreatedDate);  
         decimal a = 0;  
         a = db.Single<decimal>(query.Clone().Select(x => Sql.Sum(x.ProductValue x.Quantity (1 - x.Discount / 100))));  
         totalAmount = a;  
         query = query.Skip(pageIndex * pageSize).Take(pageSize);  
         return db.Select(query);  
       }  
     }