Queryable::Aggregate<TSource, TAccumulate, TResult> Method (IQueryable<TSource>, TAccumulate, Expression<Func<TAccumulate, TSource, TAccumulate>>, Expression<Func<TAccumulate, TResult>>)
Applies an accumulator function over a sequence. The specified seed value is used as the initial accumulator value, and the specified function is used to select the result value.
Assembly: System.Core (in System.Core.dll)
[ExtensionAttribute] public: generic<typename TSource, typename TAccumulate, typename TResult> static TResult Aggregate( IQueryable<TSource>^ source, TAccumulate seed, Expression<Func<TAccumulate, TSource, TAccumulate>^>^ func, Expression<Func<TAccumulate, TResult>^>^ selector )
Type Parameters
- TSource
The type of the elements of source.
- TAccumulate
The type of the accumulator value.
- TResult
The type of the resulting value.
Parameters
- source
- Type: System.Linq::IQueryable<TSource>
A sequence to aggregate over.
- seed
- Type: TAccumulate
The initial accumulator value.
- func
- Type: System.Linq.Expressions::Expression<Func<TAccumulate, TSource, TAccumulate>>
An accumulator function to invoke on each element.
- selector
- Type: System.Linq.Expressions::Expression<Func<TAccumulate, TResult>>
A function to transform the final accumulator value into the result value.
Return Value
Type: TResultThe transformed final accumulator value.
Usage Note
In Visual Basic and C#, you can call this method as an instance method on any object of type IQueryable<TSource>. 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).| Exception | Condition |
|---|---|
| ArgumentNullException | source or func or selector is nullptr. |
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 Aggregate<TSource, TAccumulate, TResult>(IQueryable<TSource>, TAccumulate, Expression<Func<TAccumulate, TSource, TAccumulate>>, Expression<Func<TAccumulate, TResult>>) method generates a MethodCallExpression that represents calling Aggregate<TSource, TAccumulate, TResult>(IQueryable<TSource>, TAccumulate, Expression<Func<TAccumulate, TSource, TAccumulate>>, Expression<Func<TAccumulate, TResult>>) 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 Aggregate<TSource, TAccumulate, TResult>(IQueryable<TSource>, TAccumulate, Expression<Func<TAccumulate, TSource, TAccumulate>>, Expression<Func<TAccumulate, TResult>>) depends on the implementation of the type of the source parameter. The expected behavior is that the specified function, func, is applied to each value in the source sequence and the accumulated value is returned. The seed parameter is used as the seed value for the accumulated value, which corresponds to the first parameter in func. The final accumulated value is passed to selector to obtain the result value.
To simplify common aggregation operations, the set of standard query operators also includes two counting methods, Count and LongCount, and four numeric aggregation methods, namely Max, Min, Sum, and Average.
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
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.