Array.Sort Method (Array, Int32, Int32, IComparer)
Assembly: mscorlib (in mscorlib.dll)
static member Sort : array:Array * index:int * length:int * comparer:IComparer -> unit
The starting index of the range to sort.
The number of elements in the range to sort.
array is null.
array is multidimensional.
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.
The implementation of comparer caused an error during the sort. For example, comparer might not return 0 when comparing an item with itself.
comparer is null, and one or more elements in array do not implement the IComparable interface.
If comparer is null, each element within the specified range of elements in array must implement the IComparable interface to be capable of comparisons with every other element in array.
If the sort is not successfully completed, the results are undefined.
The .NET Framework includes predefined IComparer implementations listed in the following table.
Compares any two objects, but performs a case-insensitive comparison of strings.
Compares any two objects by using the sorting conventions of the current culture.
Compares any two objects by using the sorting conventions of the invariant culture.
Compares two objects of type T by using the type's default sort order.
You can also support custom comparisons by providing an instance of your own IComparer implementation to the comparer parameter. The example does this by defining a ReverseComparer class that reverses the default sort order for instances of a type and performs case-insensitive string comparison.
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 shows how to sort the values in an Array using the default comparer and a custom comparer that reverses the sort order. Note that the result might vary depending on the current CultureInfo.
Available since 8
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Available since 8.1