Article
11/18/2011

Array.Sort<T> Method (array<T[], Int32, Int32)

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Sorts the elements in a range of elements in an Array using the IComparable<T> generic interface implementation of each element of the Array.

Namespace: System
Assembly: mscorlib (in mscorlib.dll)

Syntax

'Declaration
Public Shared Sub Sort(Of T) ( _
    array As T(), _
    index As Integer, _
    length As Integer _
)

public static void Sort<T>(
    T[] array,
    int index,
    int length
)

Type Parameters

T
The type of the elements of the array.

Parameters

array
Type: array<T[]
The one-dimensional, zero-based Array to sort

index
Type: System.Int32
The starting index of the range to sort.

length
Type: System.Int32
The number of elements in the range to sort.

Exceptions

Exception	Condition
ArgumentNullException	array is nulla null reference (Nothing in Visual Basic).
ArgumentOutOfRangeException	index is less than the lower bound of array. -or- length is less than zero.
ArgumentException	index and length do not specify a valid range in array.
InvalidOperationException	One or more elements in array do not implement the IComparable<T> generic interface.

Remarks

Each element within the specified range of elements in array must implement the IComparable<T> generic interface to be capable of comparisons with every other element in array.

If the sort is not successfully completed, the results are undefined.

This method uses the QuickSort algorithm. This implementation performs an unstable sort; that is, if two elements are equal, their order might not be preserved. In contrast, a stable sort preserves the order of elements that are equal.

On average, this method is an O(n log n) operation, where n is length; in the worst case it is an O(n ^ 2) operation.

Examples

The following code example demonstrates the Sort<T>(array<T[], Int32, Int32) generic method overload and the Sort<TKey, TValue>(array<TKey[], array<TValue[], Int32, Int32, IComparer<TKey>) generic method overload for sorting a range in an array.

The code example defines an alternative comparer for strings, named ReverseCompare, which implements the IComparer<string> (IComparer(Of String) in Visual Basic, IComparer<String^> in Visual C++) generic interface. The comparer calls the CompareTo(String) method, reversing the order of the comparands so that the strings sort high-to-low instead of low-to-high.

The code example creates and displays an array of dinosaur names, consisting of three herbivores followed by three carnivores (tyrannosaurids, to be precise). The Sort<T>(array<T[], Int32, Int32) generic method overload is used to sort the last three elements of the array, which is then displayed. The Sort<TKey, TValue>(array<TKey[], array<TValue[], Int32, Int32, IComparer<TKey>) generic method overload is used with ReverseCompare to sort the last three elements in reverse order. The thoroughly confused dinosaurs are displayed again.

Note:
The calls to the Sort<T>(array<T[], IComparer<T>) and BinarySearch<T>(array<T[], T, IComparer<T>) generic methods do not look any different from calls to their nongeneric counterparts, because Visual Basic, C#, and C++ infer the type of the generic type parameter from the type of the first argument.

Note:
To run this example, see Building Examples That Use a Demo Method and a TextBlock Control.

Imports System.Collections.Generic

Public Class ReverseComparer
   Implements IComparer(Of String)

   Public Function Compare(ByVal x As String, _
       ByVal y As String) As Integer _
       Implements IComparer(Of String).Compare

      ' Compare y and x in reverse order.
      Return y.CompareTo(x)

   End Function
End Class

Public Class Example

   Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)

      Dim dinosaurs() As String = { _
          "Pachycephalosaurus", _
          "Amargasaurus", _
          "Mamenchisaurus", _
          "Tarbosaurus", _
          "Tyrannosaurus", _
          "Albertasaurus"}

      outputBlock.Text &= vbCrLf
      For Each dinosaur As String In dinosaurs
         outputBlock.Text &= dinosaur & vbCrLf
      Next

      outputBlock.Text += String.Format(vbLf & "Sort(dinosaurs, 3, 3)") & vbCrLf
      Array.Sort(dinosaurs, 3, 3)

      outputBlock.Text &= vbCrLf
      For Each dinosaur As String In dinosaurs
         outputBlock.Text &= dinosaur & vbCrLf
      Next

      Dim rc As New ReverseComparer()

      outputBlock.Text += String.Format(vbLf & "Sort(dinosaurs, 3, 3, rc)") & vbCrLf
      Array.Sort(dinosaurs, 3, 3, rc)

      outputBlock.Text &= vbCrLf
      For Each dinosaur As String In dinosaurs
         outputBlock.Text &= dinosaur & vbCrLf
      Next

   End Sub

End Class

' This code example produces the following output:
'
'Pachycephalosaurus
'Amargasaurus
'Mamenchisaurus
'Tarbosaurus
'Tyrannosaurus
'Albertasaurus
'
'Sort(dinosaurs, 3, 3)
'
'Pachycephalosaurus
'Amargasaurus
'Mamenchisaurus
'Albertasaurus
'Tarbosaurus
'Tyrannosaurus
'
'Sort(dinosaurs, 3, 3, rc)
'
'Pachycephalosaurus
'Amargasaurus
'Mamenchisaurus
'Tyrannosaurus
'Tarbosaurus
'Albertasaurus

using System;
using System.Collections.Generic;

public class ReverseComparer : IComparer<string>
{
   public int Compare(string x, string y)
   {
      // Compare y and x in reverse order.
      return y.CompareTo(x);
   }
}

public class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      string[] dinosaurs = {"Pachycephalosaurus", 
                              "Amargasaurus", 
                              "Mamenchisaurus", 
                              "Tarbosaurus",
                              "Tyrannosaurus", 
                              "Albertasaurus"};

      outputBlock.Text += "\n";
      foreach (string dinosaur in dinosaurs)
      {
         outputBlock.Text += dinosaur + "\n";
      }

      outputBlock.Text += String.Format("\nSort(dinosaurs, 3, 3)") + "\n";
      Array.Sort(dinosaurs, 3, 3);

      outputBlock.Text += "\n";
      foreach (string dinosaur in dinosaurs)
      {
         outputBlock.Text += dinosaur + "\n";
      }

      ReverseComparer rc = new ReverseComparer();

      outputBlock.Text += String.Format("\nSort(dinosaurs, 3, 3, rc)") + "\n";
      Array.Sort(dinosaurs, 3, 3, rc);

      outputBlock.Text += "\n";
      foreach (string dinosaur in dinosaurs)
      {
         outputBlock.Text += dinosaur + "\n";
      }
   }
}

/* This code example produces the following output:

Pachycephalosaurus
Amargasaurus
Mamenchisaurus
Tarbosaurus
Tyrannosaurus
Albertasaurus

Sort(dinosaurs, 3, 3)

Pachycephalosaurus
Amargasaurus
Mamenchisaurus
Albertasaurus
Tarbosaurus
Tyrannosaurus

Sort(dinosaurs, 3, 3, rc)

Pachycephalosaurus
Amargasaurus
Mamenchisaurus
Tyrannosaurus
Tarbosaurus
Albertasaurus
 */

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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