>

>        public static decimal ComputeWeightDifference(int transactionHeaders_Id,PICSEntities context)
>        {
>            decimal emWeight = (decimal) context.EMTransactions.Where(r => (r.TransactionHeaders_Id == transactionHeaders_Id)).Sum(r => r.Weight) ?? 0;
>            decimal? detailsWeight = 0;
>            emWeight = (decimal?) context.EMTransactions.Where(r => (r.TransactionHeaders_Id == transactionHeaders_Id)).Sum(r => r.Weight) ?? 0;
>            detailsWeight = context.TransactionDetails.Where(r => (r.TransactionHeaders_Id == transactionHeaders_Id)).Sum(r => r.Weight);
>            return (decimal)(emWeight  - (decimal) (detailsWeight ?? 0);
>        }
>

>I'm really puzzled by this statement:
>

>          decimal emWeight = context.EMTransactions.Where(r => (r.TransactionHeaders_Id == transactionHeaders_Id)).Sum(r => r.Weight) ?? 0;
>

>
>It won't compile. CS0019 Operator '??' cannot be applied to operands of type 'decimal' and 'int'
>
>But this does :
>
>

>return emWeight  - (decimal) (detailsWeight ?? 0);
>

>
>So is there a way to do is in one line, or do I first need to extract the transactions and check if there are none?

Marc,
Are you sure the line with the error is exactly like:

          decimal emWeight = context.EMTransactions.Where(r => (r.TransactionHeaders_Id == transactionHeaders_Id)).Sum(r => r.Weight) ?? 0;

If yes, then you don't need the ?? at all ( actually what it is trying to say is since neither an int nor a decimal is a nullable type you can't apply ?? there). In your code I see a (decimal) casting which is an attempt to cast to decimal and that should really be a (decimal?).