How to force LINQ Sum() to return 0 while source collection is empty

Question

Basically when I do the following query, if no leads were matched the following query throws an exception. In that case I\'d prefer to have the sum equalize 0 rather than an

Answer 1

Try changing your query to this:

db.Leads.Where(l => l.Date.Day == date.Day
            && l.Date.Month == date.Month
            && l.Date.Year == date.Year
            && l.Property.Type == ProtectedPropertyType.Password
            && l.Property.PropertyId == PropertyId)
         .Select(l => l.Amount)
         .DefaultIfEmpty(0)
         .Sum();

This way, your query will only select the Amount field. If the collection is empty, it will return one element with the value of 0 and then the sum will be applied.