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

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

returnValue = source.Aggregate(func)

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

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

JScript does not support generic types or methods.

Usage Note

The Aggregate<(Of <(TSource>)>)(IEnumerable<(Of <(TSource>)>), Func<(Of <(TSource, TSource, TSource>)>)) 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>)>)(IEnumerable<(Of <(TSource>)>), Func<(Of <(TSource, TSource, TSource>)>)) passes both the element from the sequence and an aggregated value (as the first argument to func). The first element of source is used as the initial aggregate value. The result of func replaces the previous aggregated value. Aggregate<(Of <(TSource>)>)(IEnumerable<(Of <(TSource>)>), Func<(Of <(TSource, TSource, TSource>)>)) 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 build a sentence from an array of strings.

Sub AggregateEx1()
    Dim sentence As String = _
        "the quick brown fox jumps over the lazy dog"
    ' Split the string into individual words.
    Dim words() As String = sentence.Split(" "c)
    ' Prepend each word to the beginning of the new sentence to reverse the word order.
    Dim reversed As String = _
        words.Aggregate(Function(ByVal current, ByVal word) word & " " & current)

    ' Display the output.
    MsgBox(reversed)
End Sub

' This code produces the following output:
'
' dog lazy the over jumps fox brown quick the

string sentence = "the quick brown fox jumps over the lazy dog";

// Split the string into individual words.
string[] words = sentence.Split(' ');

// Prepend each word to the beginning of the 
// new sentence to reverse the word order.
string reversed = words.Aggregate((workingSentence, next) =>
                                      next + " " + workingSentence);

Console.WriteLine(reversed);

// This code produces the following output:
//
// dog lazy the over jumps fox brown quick the 

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