Enumerable.Aggregate(Of TSource) Method (IEnumerable(Of TSource), Func(Of TSource, TSource, TSource))
Applies an accumulator function over a sequence.
Assembly: System.Core (in System.Core.dll)
<ExtensionAttribute> Public Shared Function Aggregate(Of TSource) ( source As IEnumerable(Of TSource), func As Func(Of TSource, TSource, TSource) ) As TSource
System.Func(Of , , )
An accumulator function to be invoked on each element.
The final accumulator value.
The type of the elements of source.
Themethod makes it simple to perform a calculation over a sequence of values. This method works by calling func one time for each element in sourceexcept the first one. 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.
This overload of themethodisn't suitable for all casesbecause it uses the first element of source as the initial aggregate value. You should choose another overload if the return value should include only the elements of source that meet a certain condition. For example, this overload isn't reliableif you want to calculate the sum of the even numbers in source. The result will be incorrect if the first element is odd instead of even.
To simplify common aggregation operations, the standard query operators also include a general purpose count method, Count(Of TSource), and four numeric aggregation methods, namely Min, Max, Sum, and Average.
The following code example demonstrates how to reverse the order of words in a string by using.
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
Available since 8
Available since 3.5
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Available since 8.1