Array.Sort Method (Array, Array, Int32, Int32)

Sorts a range of elements in a pair of one-dimensional Array objects (one contains the keys and the other contains the corresponding items) based on the keys in the first Array using the IComparable implementation of each key.

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

'Declaration
Public Shared Sub Sort ( _
	keys As Array, _
	items As Array, _
	index As Integer, _
	length As Integer _
)

Parameters

keys
Type: System.Array

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

items
Type: System.Array

The one-dimensional Array that contains the items that correspond to each of the keys in the keys Array.

-or-

Nothing to sort only the keys Array.

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.

ExceptionCondition
ArgumentNullException

keys is Nothing.

RankException

The keys Array is multidimensional.

-or-

The items Array is multidimensional.

ArgumentOutOfRangeException

index is less than the lower bound of keys.

-or-

length is less than zero.

ArgumentException

items is not Nothing, 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 Nothing, and index and length do not specify a valid range in the items Array.

InvalidOperationException

One or more elements in the keys Array do not implement the IComparable 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.

Each key within the specified range of elements in the keys Array must implement the IComparable 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.

The following code example shows how to sort two associated arrays where the first array contains the keys and the second array contains the values. Sorts are done using the default comparer and a custom comparer that reverses the sort order. Note that the result might vary depending on the current CultureInfo.

Imports System
Imports System.Collections

Public Class SamplesArray

   Public Class myReverserClass
      Implements IComparer

      ' Calls CaseInsensitiveComparer.Compare with the parameters reversed. 
      Function Compare(x As [Object], y As [Object]) As Integer _
         Implements IComparer.Compare
         Return New CaseInsensitiveComparer().Compare(y, x)
      End Function 'IComparer.Compare

   End Class 'myReverserClass


   Public Shared Sub Main()

      ' Creates and initializes a new Array and a new custom comparer. 
      Dim myKeys As [String]() =  {"red", "GREEN", "YELLOW", "BLUE", "purple", "black", "orange"}
      Dim myValues As [String]() =  {"strawberries", "PEARS", "LIMES", "BERRIES", "grapes", "olives", "cantaloupe"}
      Dim myComparer = New myReverserClass()

      ' Displays the values of the Array.
      Console.WriteLine("The Array initially contains the following values:")
      PrintKeysAndValues(myKeys, myValues)

      ' Sorts a section of the Array using the default comparer.
      Array.Sort(myKeys, myValues, 1, 3)
      Console.WriteLine("After sorting a section of the Array using the default comparer:")
      PrintKeysAndValues(myKeys, myValues)

      ' Sorts a section of the Array using the reverse case-insensitive comparer.
      Array.Sort(myKeys, myValues, 1, 3, myComparer)
      Console.WriteLine("After sorting a section of the Array using the reverse case-insensitive comparer:")
      PrintKeysAndValues(myKeys, myValues)

      ' Sorts the entire Array using the default comparer.
      Array.Sort(myKeys, myValues)
      Console.WriteLine("After sorting the entire Array using the default comparer:")
      PrintKeysAndValues(myKeys, myValues)

      ' Sorts the entire Array using the reverse case-insensitive comparer.
      Array.Sort(myKeys, myValues, myComparer)
      Console.WriteLine("After sorting the entire Array using the reverse case-insensitive comparer:")
      PrintKeysAndValues(myKeys, myValues)

   End Sub 'Main


   Public Shared Sub PrintKeysAndValues(myKeys() As [String], myValues() As [String])

      Dim i As Integer 
      For i = 0 To myKeys.Length - 1
         Console.WriteLine("   {0,-10}: {1}", myKeys(i), myValues(i))
      Next i
      Console.WriteLine()

   End Sub 'PrintKeysAndValues

End Class 'SamplesArray


'This code produces the following output. 

'The Array initially contains the following values: 
'   red       : strawberries 
'   GREEN     : PEARS 
'   YELLOW    : LIMES 
'   BLUE      : BERRIES 
'   purple    : grapes 
'   black     : olives 
'   orange    : cantaloupe 

'After sorting a section of the Array using the default comparer: 
'   red       : strawberries 
'   BLUE      : BERRIES 
'   GREEN     : PEARS 
'   YELLOW    : LIMES 
'   purple    : grapes 
'   black     : olives 
'   orange    : cantaloupe 

'After sorting a section of the Array using the reverse case-insensitive comparer: 
'   red       : strawberries 
'   YELLOW    : LIMES 
'   GREEN     : PEARS 
'   BLUE      : BERRIES 
'   purple    : grapes 
'   black     : olives 
'   orange    : cantaloupe 

'After sorting the entire Array using the default comparer: 
'   black     : olives 
'   BLUE      : BERRIES 
'   GREEN     : PEARS 
'   orange    : cantaloupe 
'   purple    : grapes 
'   red       : strawberries 
'   YELLOW    : LIMES 

'After sorting the entire Array using the reverse case-insensitive comparer: 
'   YELLOW    : LIMES 
'   red       : strawberries 
'   purple    : grapes 
'   orange    : cantaloupe 
'   GREEN     : PEARS 
'   BLUE      : BERRIES 
'   black     : olives

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

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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