Question

I was getting an error when I was execting the following query that summed a non-nullable decimal. The magnitude was null when there was no magnitude value for a location/organization combination.

let q = query { from m in Measure do
                  where (locations.Contains(m.Location) 
                         && organizations.Contains(m.Organization))
                  sumBy m.Magnitude }

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

I solved this in the following way. Is this there a better way to do this?

let convert (n:Nullable<decimal>) =
        let c:decimal = 0M
        if n.HasValue then n.Value else c

let q = query { from m in Measure do
                  let nullable = Nullable<decimal>(m.Magnitude)
                  where (locations.Contains(m.Location) 
                         && organizations.Contains(m.Organization))
                  sumBy (convert(nullable)) }

Thanks. I changed my query to the following.

query {  for m in db.Measurement do
                let nullable = Nullable<decimal>(m.Magnitude)
                where ( m.Measure = me 
                        && (if slice.Organization > 0L then organizationUnits.Contains( m.PrimalOrganizationUnit.Value ) else true)
                        && (if slice.Location > 0L then locationUnits.Contains(m.PrimalLocationUnit.Value) else true) )
                sumByNullable (nullable) }

Answer 1

sumByNullable?