Question

When using sum with lambda in Linq to SQL using the following code:

int query = (from f in odc.RDetails
                     where f.ticketID == int.Parse(ticket.ToString())
                     select f).Sum(x => x.Rate);

I get the following error:

The null value cannot be assigned to a member with type System.Int32 which is a non-nullable value type.

Answer 1

. You have to make sure x.Rate is an int, and not an int? (an int that accepts null as a value).

. If the query has no elements, .Sum won’t do anything and will return null. Choose a default value, let’s say 0.

var query = from f in odc.RDetails
            where f.ticketID == int.Parse(ticket.ToString())
            select f;

int result = query.Any() 
             ? query.Sum(x => x.Rate ?? 0) // use the ?? if x.Rate is an "int?".
             : 0; // default value you can choose.