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.

Namespace:  System.Linq
Assembly:  System.Core (in System.Core.dll)

static member Aggregate : 
        source:IQueryable<'TSource> * 
        seed:'TAccumulate * 
        func:Expression<Func<'TAccumulate, 'TSource, 'TAccumulate>> * 
        selector:Expression<Func<'TAccumulate, 'TResult>> -> 'TResult 

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: TResult
The 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).

ExceptionCondition
ArgumentNullException

source or func or selector is a null reference (Nothing in Visual Basic).

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.

The following code example demonstrates how to use Aggregate(TSource, TAccumulate, TResult)(IQueryable(TSource), TAccumulate, Expression(Func(TAccumulate, TSource, TAccumulate)), Expression(Func(TAccumulate, TResult))) to apply an accumulator function and a result selector.

No code example is currently available or this language may not be supported.

.NET Framework

Supported in: 4.5, 4, 3.5

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone Silverlight 8.1, Windows Phone Silverlight 8

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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