Array.Sort<'T> Method ('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)

static member Sort<'T> : 
        array:'T[] *
        index:int *
        length:int -> unit


Type: 'T[]

The one-dimensional, zero-based Array to sort

Type: System.Int32

The starting index of the range to sort.

Type: System.Int32

The number of elements in the range to sort.

Type Parameters


The type of the elements of the array.

Exception Condition

array is null.


index is less than the lower bound of array.


length is less than zero.


index and length do not specify a valid range in array.


One or more elements in array do not implement the IComparable<'T> generic interface.

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 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.

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.


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 (IL Disassembler) to examine the Microsoft intermediate language (MSIL), you can see that the generic methods are being called.

No code example is currently available or this language may not be supported.

Universal Windows Platform
Available since 8
.NET Framework
Available since 2.0
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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