Queryable::Aggregate<TSource> Method (IQueryable<TSource>^, Expression<Func<TSource, TSource, TSource>^>^)

.NET Framework (current version)

Applies an accumulator function over a sequence.

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

Syntax

public:
generic<typename TSource>
[ExtensionAttribute]
static TSource Aggregate(
	IQueryable<TSource>^ source,
	Expression<Func<TSource, TSource, TSource>^>^ func
)

Parameters

source: Type: System.Linq::IQueryable<TSource>^
A sequence to aggregate over.

func: Type: System.Linq.Expressions::Expression<Func<TSource, TSource, TSource>^>^
An accumulator function to apply to each element.

Return Value

Type: TSource

The final accumulator value.

Type Parameters

TSource: The type of the elements of source.

Exceptions

Exception	Condition
ArgumentNullException	source or func is null.
InvalidOperationException	source contains no elements.

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>(IQueryable<TSource>^, Expression<Func<TSource, TSource, TSource>^>^) method generates a MethodCallExpression that represents calling Aggregate<TSource>(IQueryable<TSource>^, Expression<Func<TSource, TSource, TSource>^>^) 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>(IQueryable<TSource>^, Expression<Func<TSource, TSource, TSource>^>^) 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 first value in source is used as the seed value for the accumulated value, which corresponds to the first parameter in func.

To simplify common aggregation operations, the set of standard query operators also includes two counting methods, Count<TSource> and LongCount<TSource>, and four numeric aggregation methods, namely Max<TSource>, Min<TSource>, Sum, and Average.

Examples

The following code example demonstrates how to use Aggregate<TSource>(IQueryable<TSource>^, Expression<Func<TSource, TSource, TSource>^>^) to build a sentence from an array of strings.

C++

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

Version Information

Universal Windows Platform
Available since 8
.NET Framework
Available since 3.5
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.1
Windows Phone
Available since 8.1