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

Sorts 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)

static member Sort : 
        keys:'TKey[] * 
        items:'TValue[] * 
        comparer:IComparer<'TKey> -> unit 

Type Parameters


The type of the elements of the key array.


The type of the elements of the items array.


Type: TKey[]
The one-dimensional, zero-based Array that contains the keys to sort.
Type: TValue[]
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.
Type: System.Collections.Generic.IComparer(TKey)
The IComparer(T) generic interface implementation to use when comparing elements, or a null reference (Nothing in Visual Basic) to use the IComparable(T) generic interface implementation of each element.


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.


comparer is a null reference (Nothing in Visual Basic), 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 a null reference (Nothing in Visual Basic), each key 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 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 the Length of array; in the worst case it is an O(n ^ 2) operation.

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:


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 (MSIL 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.

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

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.