Articolo
11/18/2011

Enumerable.Max<TSource, TResult> Method (IEnumerable<TSource>, Func<TSource, TResult>)

Microsoft Silverlight will reach end of support after October 2021. Learn more.

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

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

Syntax

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

public static TResult Max<TSource, TResult>(
    this IEnumerable<TSource> source,
    Func<TSource, TResult> selector
)

Type Parameters

TSource
The type of the elements of source.

TResult
The type of the value returned by selector.

Parameters

source
Type: System.Collections.Generic.IEnumerable<TSource>
A sequence of values to determine the maximum value of.

selector
Type: System.Func<TSource, TResult>
A transform function to apply to each element.

Return Value

Type: TResult
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<TSource>. When you use instance method syntax to call this method, omit the first parameter.

Exceptions

Exception	Condition
ArgumentNullException	source or selector is nulla null reference (Nothing in Visual Basic).

Remarks

If type TResult implements IComparable<T>, this method uses that implementation to compare values. Otherwise, if type TResult implements IComparable, that implementation is used to compare values.

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

Examples

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

Note:
This code example uses an overload of this overloaded method that is different from the specific overload that this topic describes. To extend the example to this topic, change the body of the selector function.

   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

      class Pet
      {
         public string Name { get; set; }
         public int Age { get; set; }
      }

      public static void MaxEx4()
      {
         Pet[] pets = { new Pet { Name="Barley", Age=8 },
                            new Pet { Name="Boots", Age=4 },
                            new Pet { Name="Whiskers", Age=1 } };

         int max = pets.Max(pet => pet.Age + pet.Name.Length);

         outputBlock.Text += String.Format(
             "The maximum pet age plus name length is {0}.",
             max) + "\n";
      }

      /*
       This code produces the following output:

       The maximum pet age plus name length is 14.
      */

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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