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

Sorts a range of elements in a pair of Array objects (one contains the keys and the other contains the corresponding items) based on the keys in the first Array using the specified IComparer<T> generic interface.

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

public static void Sort<TKey, TValue>(
	TKey[] keys,
	TValue[] items,
	int index,
	int length,
	IComparer<TKey> comparer
)

Type Parameters

TKey

The type of the elements of the key array.

TValue

The type of the elements of the items array.

Parameters

keys
Type: TKey[]

The one-dimensional, zero-based Array that contains the keys to sort.

items
Type: TValue[]

The one-dimensional, zero-based Array that contains the items that correspond to the keys in keys, or null to sort only keys.

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<TKey>

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

keys is null.

ArgumentOutOfRangeException

index is less than the lower bound of keys.

-or-

length is less than zero.

ArgumentException

items is not null, and the lower bound of keys does not match the lower bound of items.

-or-

items is not null, and the length of keys is greater than the length of items.

-or-

index and length do not specify a valid range in the keys Array.

-or-

items is not null, and index and length do not specify a valid range in the items 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 the keys Array do not implement the IComparable<T> generic interface.

Each key in the keys Array has a corresponding item in the items Array. When a key is repositioned during the sorting, the corresponding item in the items Array is similarly repositioned. Therefore, the items Array is sorted according to the arrangement of the corresponding keys in the keys Array.

If comparer is null, each key within the specified range of elements in the keys Array must implement the IComparable<T> generic interface to be capable of comparisons with every other key.

You can sort if there are more items than keys, but the items that have no corresponding keys will not be sorted. You cannot sort if there are more keys than items; doing this throws an ArgumentException.

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

This method uses the introspective sort (introsort) algorithm as follows:

  • If the partition size is fewer than 16 elements, it uses an insertion sort algorithm.

  • If the number of partitions exceeds 2 * LogN, where N is the range of the input array, it uses a Heapsort algorithm.

  • Otherwise, it uses a 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.

For arrays that are sorted by using the Heapsort and Quicksort algorithms, in the worst case, this method is an O(n log n) operation, where n is length.

Notes to Callers

The .NET Framework 4 and earlier versions used only the Quicksort algorithm. Quicksort identifies invalid comparers in some situations in which the sorting operation throws an IndexOutOfRangeException exception, and throws an ArgumentException exception to the caller. Starting with the .NET Framework 4.5, it is possible that sorting operations that previously threw ArgumentException will not throw an exception, because the insertion sort and heapsort algorithms do not detect an invalid comparer. For the most part, this applies to arrays with fewer than 16 elements.

The following code example demonstrates the Sort<TKey, TValue>(TKey[], TValue[]), Sort<TKey, TValue>(TKey[], TValue[], IComparer<TKey>), Sort<TKey, TValue>(TKey[], TValue[], Int32, Int32), and Sort<TKey, TValue>(TKey[], TValue[], Int32, Int32, IComparer<TKey>) generic method overloads, for sorting pairs of arrays that represent keys and values.

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 (the keys) and an array of integers representing the maximum length of each dinosaur in meters (the values). The arrays are then sorted and displayed several times:

NoteNote

The calls to the 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 two arguments. If you use the Ildasm.exe (IL 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 = {
            "Seismosaurus", 
            "Chasmosaurus", 
            "Coelophysis", 
            "Mamenchisaurus", 
            "Caudipteryx", 
            "Cetiosaurus"  };

        int[] dinosaurSizes = { 40, 5, 3, 22, 1, 18 };

        Console.WriteLine();
        for (int i = 0; i < dinosaurs.Length; i++)
        {
            Console.WriteLine("{0}: up to {1} meters long.", 
                dinosaurs[i], dinosaurSizes[i]);
        }

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

        Console.WriteLine();
        for (int i = 0; i < dinosaurs.Length; i++)
        {
            Console.WriteLine("{0}: up to {1} meters long.", 
                dinosaurs[i], dinosaurSizes[i]);
        }

        ReverseComparer rc = new ReverseComparer();

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

        Console.WriteLine();
        for (int i = 0; i < dinosaurs.Length; i++)
        {
            Console.WriteLine("{0}: up to {1} meters long.", 
                dinosaurs[i], dinosaurSizes[i]);
        }

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

        Console.WriteLine();
        for (int i = 0; i < dinosaurs.Length; i++)
        {
            Console.WriteLine("{0}: up to {1} meters long.", 
                dinosaurs[i], dinosaurSizes[i]);
        }

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

        Console.WriteLine();
        for (int i = 0; i < dinosaurs.Length; i++)
        {
            Console.WriteLine("{0}: up to {1} meters long.", 
                dinosaurs[i], dinosaurSizes[i]);
        }
    }
}

/* This code example produces the following output:

Seismosaurus: up to 40 meters long.
Chasmosaurus: up to 5 meters long.
Coelophysis: up to 3 meters long.
Mamenchisaurus: up to 22 meters long.
Caudipteryx: up to 1 meters long.
Cetiosaurus: up to 18 meters long.

Sort(dinosaurs, dinosaurSizes)

Caudipteryx: up to 1 meters long.
Cetiosaurus: up to 18 meters long.
Chasmosaurus: up to 5 meters long.
Coelophysis: up to 3 meters long.
Mamenchisaurus: up to 22 meters long.
Seismosaurus: up to 40 meters long.

Sort(dinosaurs, dinosaurSizes, rc)

Seismosaurus: up to 40 meters long.
Mamenchisaurus: up to 22 meters long.
Coelophysis: up to 3 meters long.
Chasmosaurus: up to 5 meters long.
Cetiosaurus: up to 18 meters long.
Caudipteryx: up to 1 meters long.

Sort(dinosaurs, dinosaurSizes, 3, 3)

Seismosaurus: up to 40 meters long.
Mamenchisaurus: up to 22 meters long.
Coelophysis: up to 3 meters long.
Caudipteryx: up to 1 meters long.
Cetiosaurus: up to 18 meters long.
Chasmosaurus: up to 5 meters long.

Sort(dinosaurs, dinosaurSizes, 3, 3, rc)

Seismosaurus: up to 40 meters long.
Mamenchisaurus: up to 22 meters long.
Coelophysis: up to 3 meters long.
Chasmosaurus: up to 5 meters long.
Cetiosaurus: up to 18 meters long.
Caudipteryx: up to 1 meters long.
 */

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone 8, Silverlight 8.1

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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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