Udostępnij za pośrednictwem

  • Artykuł

Enumerable.Max<TSource> Method (IEnumerable<TSource>)

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

Returns the maximum value in a generic sequence.

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

Syntax

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

public static TSource Max<TSource>(
    this IEnumerable<TSource> source
)

Type Parameters

  • TSource
    The type of the elements of source.

Parameters

Return Value

Type: TSource
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 is nulla null reference (Nothing in Visual Basic).

Remarks

If type TSource implements IComparable<T>, the Max<TSource>(IEnumerable<TSource>) method uses that implementation to compare values. Otherwise, if type TSource implements IComparable, that implementation is used to compare values.

If TSource is a reference type and the source sequence is empty or contains only values that are nulla null reference (Nothing in Visual Basic), this method returns nulla null reference (Nothing in Visual Basic).

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>) to determine the maximum value in a sequence of IComparable<T> objects.

   ' This class implements IComparable 
   ' and has a custom 'CompareTo' implementation.
   Class Pet
      Implements IComparable(Of Pet)

      Public Name As String
      Public Age As Integer

      ''' <summary>
      ''' Compares Pet objects by the sum of their age and name length.
      ''' </summary>
      ''' <param name="other">The Pet to compare this Pet to.</param>
      ''' <returns>-1 if this Pet's sum is 'less' than the other Pet,
      ''' 0 if they are equal,
      ''' or 1 if this Pet's sum is 'greater' than the other Pet.</returns>
      Function CompareTo(ByVal other As Pet) As Integer _
          Implements IComparable(Of Pet).CompareTo

         If (other.Age + other.Name.Length > Me.Age + Me.Name.Length) Then
            Return -1
         ElseIf (other.Age + other.Name.Length = Me.Age + Me.Name.Length) Then
            Return 0
         Else
            Return 1
         End If
      End Function
   End Class

   Sub MaxEx3()
      ' 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}}

      ' Find the "maximum" pet according to the 
      ' custom CompareTo() implementation.
      Dim max As Pet = pets.Max()

      ' Display the result.
      outputBlock.Text &= "The 'maximum' animal is " & max.Name & vbCrLf
   End Sub

   ' This code produces the following output:
   '
   ' The 'maximum' animal is Barley


      /// <summary>
      /// This class implements IComparable to be able to 
      /// compare one Pet to another Pet.
      /// </summary>
      class Pet : IComparable<Pet>
      {
         public string Name { get; set; }
         public int Age { get; set; }

         /// <summary>
         /// Compares this Pet to another Pet by 
         /// summing each Pet's age and name length.
         /// </summary>
         /// <param name="other">The Pet to compare this Pet to.</param>
         /// <returns>-1 if this Pet is 'less' than the other Pet, 
         /// 0 if they are equal,
         /// or 1 if this Pet is 'greater' than the other Pet.</returns>
         int IComparable<Pet>.CompareTo(Pet other)
         {
            int sumOther = other.Age + other.Name.Length;
            int sumThis = this.Age + this.Name.Length;

            if (sumOther > sumThis)
               return -1;
            else if (sumOther == sumThis)
               return 0;
            else
               return 1;
         }
      }

      public static void MaxEx3()
      {
         Pet[] pets = { new Pet { Name="Barley", Age=8 },
                            new Pet { Name="Boots", Age=4 },
                            new Pet { Name="Whiskers", Age=1 } };

         Pet max = pets.Max();

         outputBlock.Text += String.Format(
             "The 'maximum' animal is {0}.",
             max.Name) + "\n";
      }

      /*
       This code produces the following output:

       The 'maximum' animal is Barley.
      */

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.