<ExtensionAttribute> _
Public Shared Function Aggregate(Of TSource, TAccumulate) ( _
    source As IEnumerable(Of TSource), _
    seed As TAccumulate, _
    func As Func(Of TAccumulate, TSource, TAccumulate) _
) As TAccumulate

Dim source As IEnumerable(Of TSource)
Dim seed As TAccumulate
Dim func As Func(Of TAccumulate, TSource, TAccumulate)
Dim returnValue As TAccumulate

returnValue = source.Aggregate(seed, _
    func)

public static TAccumulate Aggregate<TSource, TAccumulate>(
    this IEnumerable<TSource> source,
    TAccumulate seed,
    Func<TAccumulate, TSource, TAccumulate> func
)

[ExtensionAttribute]
public:
generic<typename TSource, typename TAccumulate>
static TAccumulate Aggregate(
    IEnumerable<TSource>^ source, 
    TAccumulate seed, 
    Func<TAccumulate, TSource, TAccumulate>^ func
)

JScript does not support generic types or methods.

Usage Note

The Aggregate<(Of <(TSource, TAccumulate>)>)(IEnumerable<(Of <(TSource>)>), TAccumulate, Func<(Of <(TAccumulate, TSource, TAccumulate>)>)) method makes it simple to perform a calculation over a sequence of values. This method works by calling func one time for each element in source. Each time func is called, Aggregate<(Of <(TSource, TAccumulate>)>)(IEnumerable<(Of <(TSource>)>), TAccumulate, Func<(Of <(TAccumulate, TSource, TAccumulate>)>)) passes both the element from the sequence and an aggregated value (as the first argument to func). The value of the seed parameter is used as the initial aggregate value. The result of func replaces the previous aggregated value. Aggregate<(Of <(TSource, TAccumulate>)>)(IEnumerable<(Of <(TSource>)>), TAccumulate, Func<(Of <(TAccumulate, TSource, TAccumulate>)>)) returns the final result of func.

To simplify common aggregation operations, the standard query operators also include a general purpose count method, Count, and four numeric aggregation methods, namely Min, Max, Sum, and Average.

The following code example demonstrates how to use Aggregate to apply an accumulator function and use a seed value.

Sub AggregateEx2()
    ' Create an array of Integers.
    Dim ints() As Integer = {4, 8, 8, 3, 9, 0, 7, 8, 2}

    ' Count the even numbers in the array, using a seed value of 0.
    Dim numEven As Integer = _
        ints.Aggregate(0, _
                       Function(ByVal total, ByVal number) _
                           IIf(number Mod 2 = 0, total + 1, total))

    ' Display the output.
    MsgBox("The number of even integers is " & numEven)
End Sub

' This code produces the following output:
'
'The number of even integers is 6

int[] ints = { 4, 8, 8, 3, 9, 0, 7, 8, 2 };

// Count the even numbers in the array, using a seed value of 0.
int numEven = ints.Aggregate(0, (total, next) =>
                                    next % 2 == 0 ? total + 1 : total);

Console.WriteLine("The number of even integers is: {0}", numEven);

// This code produces the following output:
//
// The number of even integers is: 6 

Windows 7, Windows Vista, Windows XP SP2, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

.NET Framework

.NET Compact Framework

XNA Framework

Reference