Queryable::Sum<TSource> Method (IQueryable<TSource>, Expression<Func<TSource, Nullable<Single>>>)
Computes the sum of the sequence of nullable Single values that is obtained by invoking a projection function on each element of the input sequence.
Assembly: System.Core (in System.Core.dll)
[ExtensionAttribute] public: generic<typename TSource> static Nullable<float> Sum( IQueryable<TSource>^ source, Expression<Func<TSource, Nullable<float>>^>^ selector )
The type of the elements of source.
- Type: System.Linq::IQueryable<>
A sequence of values of type TSource.
Usage NoteIn Visual Basic and C#, you can call this method as an instance method on any object of type IQueryable<>. When you use instance method syntax to call this method, omit the first parameter. For more information, see Extension Methods (Visual Basic) or Extension Methods (C# Programming Guide).
This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T, TResult> types. For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.
The method generates a MethodCallExpression that represents calling itself as a constructed generic method. It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.
The query behavior that occurs as a result of executing an expression tree that represents calling depends on the implementation of the type of the source parameter. The expected behavior is that it invokes selector on each element of source and returns the sum of the resulting values.
The following code example demonstrates how to use Sum<TSource>(IQueryable<TSource>, Expression<Func<TSource, Double>>) to sum the projected values of a sequence.
This code example uses an overload of this overloaded method that is different from the specific overload that this topic describes. To extend the example to this topic, change the body of the selector function.
Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2