Question

Sorry if this has already been asked somewhere, but I wasn’t able to find it. It seems that Average and Sum do not work across anonymous types. I’ve been trying for a while to get this code to work, with no luck. The query I’m doing is:

var trainingPlan = (from tp in context.TPM_TRAININGPLAN
                    join tpd in context.TPM_TRAININGPLANDELIVERABLES on tp.TRAININGPLANID equals tpd.TRAININGPLANID
                    join t in context.TPM_TASK on tpd.TASKID equals t.TASKID
                    where tp.TPM_PROJECTVERSION.PROJECTID == projectId && tp.TPM_PROJECTVERSION.VERSIONID == versionId && tp.TRAININGPLANTYPE == "prescribed"
                    select new
                    {
                        CourseLength = tp.COURSELENGTHHOUR * 60 + tp.COURSELENGTHMINUTE,
                        DeliveryMethod = tp.TPM_DELIVERYMETHODS.NAME,
                        CourseCode = t.COURSECODE
                    });

I now want to take an sum of the CourseLength property, so I do:

int sum = trainingPlan.Sum(l => l.CourseLength.Value);

However, “sum” ends up being 0. Same with “Average”. I can clearly see under the debugger that trainingPlan has two items, one with CourseLength = 90 and one with CourseLength = 150.

Does Sum just not work on these types of enumerables? Thanks!

Answer 1

Definitely this could be an issue with the database provider? Since this is a small collection, and you could do trainingPlan.AsEnumerable().Sum. Or, if you are doing multiple calculations, do trainingPlan.ToList(), store that and use it in your calculations.