Enumerable.Max(Of TSource) Method (IEnumerable(Of TSource), Func(Of TSource, Int32))

May 11, 2014

Invokes a transform function on each element of a sequence and returns the maximum Int32 value.

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

'Declaration
<ExtensionAttribute> _
Public Shared Function Max(Of TSource) ( _
	source As IEnumerable(Of TSource), _
	selector As Func(Of TSource, Integer) _
) As Integer

Type Parameters

TSource

The type of the elements of source.

Parameters

source
Type: System.Collections.Generic.IEnumerable(Of TSource)
A sequence of values to determine the maximum value of.
selector
Type: System.Func(Of TSource, Int32)
A transform function to apply to each element.

Return Value

Type: System.Int32
The maximum value in the sequence.

Usage Note

In Visual Basic and C#, you can call this method as an instance method on any object of type IEnumerable(Of TSource). When you use instance method syntax to call this method, omit the first parameter.

ExceptionCondition
ArgumentNullException

source or selector is Nothing.

InvalidOperationException

source contains no elements.

The Max(Of TSource)(IEnumerable(Of TSource), Func(Of TSource, Int32)) method uses the Int32 implementation of IComparable(Of T) to compare values.

You can apply this method to a sequence of arbitrary values if you provide a function, selector, that projects the members of source into a numeric type, specifically Int32.

In Visual Basic query expression syntax, an Aggregate Into Max() clause translates to an invocation of Enumerable.Max.

The following code example demonstrates how to use Max(Of TSource)(IEnumerable(Of TSource), Func(Of TSource, Int32)) to determine the maximum value in a sequence of projected values.


   Structure Pet
      Public Name As String
      Public Age As Integer
   End Structure

   Sub MaxEx4()
      ' Create an array of Pet objects.
      Dim pets() As Pet = {New Pet With {.Name = "Barley", .Age = 8}, _
                           New Pet With {.Name = "Boots", .Age = 4}, _
                           New Pet With {.Name = "Whiskers", .Age = 1}}

      ' Determine the "maximum" pet by passing a
      ' lambda expression to Max() that sums the pet's age
      ' and name length.
      Dim max As Integer = pets.Max(Function(pet) _
                                        pet.Age + pet.Name.Length)

      ' Display the result.
      outputBlock.Text &= "The maximum pet age plus name length is " & max & vbCrLf
   End Sub

   ' This code produces the following output:
   '
   ' The maximum pet age plus name length is 14



Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

Windows Phone

Show:
© 2014 Microsoft