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

Sorts the elements in a range of elements in an Array using the specified IComparer<T> generic interface.

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

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

Type Parameters

T

The type of the elements of the array.

Parameters

array
Type: 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.
comparer
Type: System.Collections.Generic.IComparer<T>
The IComparer<T> generic interface implementation to use when comparing elements, or null to use the IComparable<T> generic interface implementation of each element.

ExceptionCondition
ArgumentNullException

array is null.

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.

-or-

The implementation of comparer caused an error during the sort. For example, comparer might not return 0 when comparing an item with itself.

InvalidOperationException

comparer is null, and one or more elements in array do not implement the IComparable<T> generic interface.

If comparer is null, 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.

The following code example demonstrates the Sort<T>(T[], Int32, Int32) generic method overload and the Sort<TKey, TValue>(TKey[], 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>(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>(TKey[], 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.

NoteNote

The calls to the Sort<T>(T[], IComparer<T>) and BinarySearch<T>(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. If you use the Ildasm.exe (MSIL Disassembler) to examine the Microsoft intermediate language (MSIL), you can see that the generic methods are being called.


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 Main()
    {
        string[] dinosaurs = {"Pachycephalosaurus", 
                              "Amargasaurus", 
                              "Mamenchisaurus", 
                              "Tarbosaurus",
                              "Tyrannosaurus", 
                              "Albertasaurus"};

        Console.WriteLine();
        foreach( string dinosaur in dinosaurs )
        {
            Console.WriteLine(dinosaur);
        }

        Console.WriteLine("\nSort(dinosaurs, 3, 3)");
        Array.Sort(dinosaurs, 3, 3);

        Console.WriteLine();
        foreach( string dinosaur in dinosaurs )
        {
            Console.WriteLine(dinosaur);
        }

        ReverseComparer rc = new ReverseComparer();

        Console.WriteLine("\nSort(dinosaurs, 3, 3, rc)");
        Array.Sort(dinosaurs, 3, 3, rc);

        Console.WriteLine();
        foreach( string dinosaur in dinosaurs )
        {
            Console.WriteLine(dinosaur);
        }
    }
}

/* 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
 */


.NET Framework

Supported in: 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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