Enumerable.Aggregate(Of TSource) Method (IEnumerable(Of TSource), Func(Of TSource, TSource, TSource))
[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]
Applies an accumulator function over a sequence.
Assembly: System.Core (in System.Core.dll)
'Declaration <ExtensionAttribute> _ Public Shared Function Aggregate(Of TSource) ( _ source As IEnumerable(Of TSource), _ func As Func(Of TSource, TSource, TSource) _ ) As TSource
The type of the elements of source.
- Type: System.Func(Of , , )
An accumulator function to be invoked on each element.
The final accumulator value.
Usage NoteIn Visual Basic and C#, you can call this method as an instance method on any object of type IEnumerable(Of ). When you use instance method syntax to call this method, omit the first parameter.
The 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, 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. returns the final result of func.
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(current, word) word & " " & current) ' Display the output. outputBlock.Text += reversed + vbCrLf End Sub ' This code produces the following output: ' ' dog lazy the over jumps fox brown quick the