Array.Sort(TKey, TValue) Method (TKey, TValue, IComparer(TKey))
Assembly: mscorlib (in mscorlib.dll)
static member Sort : keys:'TKey * items:'TValue * comparer:IComparer<'TKey> -> unit
The type of the elements of the key array.
The type of the elements of the items array.
- Type: 
The one-dimensional, zero-based Array that contains the keys to sort.
- Type: 
The one-dimensional, zero-based Array that contains the items that correspond to the keys in keys, or a null reference (Nothing in Visual Basic) to sort only keys.
keys is a null reference (Nothing in Visual Basic).
items is not a null reference (Nothing in Visual Basic), and the lower bound of keys does not match the lower bound of items.
items is not a null reference (Nothing in Visual Basic), and the length of keys is greater than the length of items.
The implementation of comparer caused an error during the sort. For example, comparer might not return 0 when comparing an item with itself.
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.
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 the Length of array.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, 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:
The Sort(TKey, TValue)(TKey, TValue) overload is used to sort both arrays in order of the dinosaur names in the first array.
The overload and an instance of ReverseCompare are used to reverse the sort order of the paired arrays.
The Sort(TKey, TValue)(TKey, TValue, Int32, Int32) overload is used to sort the last three elements of both arrays.
The Sort(TKey, TValue)(TKey, TValue, Int32, Int32, IComparer(TKey)) overload is used to sort the last three elements of both arrays in reverse order.
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.