Hello, Vahid!
Yes, I know... the problem is that Value is not a nullable type; what
happens is that there are no elements to sum, the same happens when
using SQL: "SELECT SUM(Value) FROM AnalogicalValue WHERE 1 = 2"
returns NULL.
I solved my problem with:
Object result = session.CreateQuery("select sum(a.Value) from
AnalogicalValue a").UniqueResult();
Int32 sum = result is Int32 ? (Int32) result : 0;
RP
session.CreateQuery("select sum(a.Value) from AnalogicalValue
a").SetParameter("anmid", (Int32)
AnalogicalElementMeasure.ActivePower).UniqueResult();
On Apr 14, 4:42 pm, Vahid <[email protected]> wrote:
> Hello,
> This is the definition of Sum method here:
> public static ***TResult*** Sum<TSource>(
> this IQueryable<TSource> source,
> Expression<Func<TSource, ***TResult***>> selector)
>
> As you can see "TResult" defines the return type of the method based
> on the result of the applying a lambda-expression which is TResult
> too.
> Now try queries like this : (the same rule applies to EF and LINQ to
> SQL)
> var sum = ....Where(t=>...)
> .Sum(t=>(decimal?)t.Value)??0; //using nullable types
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