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ArrayList.Sort Method (IComparer)

Sorts the elements in the entire ArrayList using the specified comparer.

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

'Declaration
Public Overridable Sub Sort ( _
	comparer As IComparer _
)
'Usage
Dim instance As ArrayList
Dim comparer As IComparer

instance.Sort(comparer)
public void Sort (
	IComparer comparer
)
public function Sort (
	comparer : IComparer
)
Not applicable.

Parameters

comparer

The IComparer implementation to use when comparing elements.

-or-

a null reference (Nothing in Visual Basic) to use the IComparable implementation of each element.

Exception typeCondition

NotSupportedException

The ArrayList is read-only.

If comparer is set to a null reference (Nothing in Visual Basic), then this method 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. To perform a stable sort you must implement a custom IComparer.

On average, this method is an O(n log n) operation, where n is Count; in the worst case it is an O(n^2) operation.

The following code example shows how to sort the values in an ArrayList using the default comparer and a custom comparer that reverses the sort order.

Imports System
Imports System.Collections
Imports Microsoft.VisualBasic

Public Class SamplesArrayList

   Public Class myReverserClass
      Implements IComparer

      ' Calls CaseInsensitiveComparer.Compare with the parameters reversed.
      Public Function Compare( ByVal x As Object, ByVal 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 ArrayList.
      Dim myAL As New ArrayList()
      myAL.Add("The")
      myAL.Add("quick")
      myAL.Add("brown")
      myAL.Add("fox")
      myAL.Add("jumps")
      myAL.Add("over")
      myAL.Add("the")
      myAL.Add("lazy")
      myAL.Add("dog")

      ' Displays the values of the ArrayList.
      Console.WriteLine("The ArrayList initially contains the following values:")
      PrintIndexAndValues(myAL)

      ' Sorts the values of the ArrayList using the default comparer.
      myAL.Sort()
      Console.WriteLine("After sorting with the default comparer:")
      PrintIndexAndValues(myAL)

      ' Sorts the values of the ArrayList using the reverse case-insensitive comparer.
      Dim myComparer = New myReverserClass()
      myAL.Sort(myComparer)
      Console.WriteLine("After sorting with the reverse case-insensitive comparer:")
      PrintIndexAndValues(myAL)

   End Sub 'Main

   Public Shared Sub PrintIndexAndValues(myList As IEnumerable)
      Dim i As Integer = 0
      Dim obj As [Object]
      For Each obj In  myList
         Console.WriteLine(vbTab + "[{0}]:" + vbTab + "{1}", i, obj)
         i = i + 1
      Next obj
      Console.WriteLine()
   End Sub 'PrintIndexAndValues

End Class 'SamplesArrayList


'This code produces the following output.
'The ArrayList initially contains the following values:
'        [0]:    The
'        [1]:    quick
'        [2]:    brown
'        [3]:    fox
'        [4]:    jumps
'        [5]:    over
'        [6]:    the
'        [7]:    lazy
'        [8]:    dog
'
'After sorting with the default comparer:
'        [0]:    brown
'        [1]:    dog
'        [2]:    fox
'        [3]:    jumps
'        [4]:    lazy
'        [5]:    over
'        [6]:    quick
'        [7]:    the
'        [8]:    The
'
'After sorting with the reverse case-insensitive comparer:
'        [0]:    the
'        [1]:    The
'        [2]:    quick
'        [3]:    over
'        [4]:    lazy
'        [5]:    jumps
'        [6]:    fox
'        [7]:    dog
'        [8]:    brown


import System.*;
import System.Collections.*;

public class SamplesArrayList
{
    public static class MyReverserClass implements IComparer
    {
        // Calls CaseInsensitiveComparer.Compare with the parameters reversed.
        public int Compare(Object x, Object y)
        {
            return(new CaseInsensitiveComparer()).Compare(y, x) ;
        } //IComparer.Compare
    } //MyReverserClass
    
    public static void main(String[] args) 
    {
        // Creates and initializes a new ArrayList.
        ArrayList myAL =  new ArrayList();
        myAL.Add("The");
        myAL.Add("quick");
        myAL.Add("brown");
        myAL.Add("fox");
        myAL.Add("jumps");
        myAL.Add("over");
        myAL.Add("the");
        myAL.Add("lazy");
        myAL.Add("dog");
          
        // Displays the values of the ArrayList.
        Console.WriteLine("The ArrayList initially contains the following"
            + " values:");
        PrintIndexAndValues(myAL); 
          
        // Sorts the values of the ArrayList using the default comparer.
        myAL.Sort();
        Console.WriteLine("After sorting with the default comparer:");
        PrintIndexAndValues(myAL);
          
        // Sorts the values of the ArrayList using the reverse case-insensitive
        // comparer.
        IComparer myComparer = new MyReverserClass();
        myAL.Sort(myComparer);
        Console.WriteLine("After sorting with the reverse case-insensitive"
            + " comparer:");
        PrintIndexAndValues(myAL);
    } //main
       
    public static void PrintIndexAndValues(IEnumerable myList) 
    {
        int i = 0;
        IEnumerator objEnum = myList.GetEnumerator();
        while (objEnum.MoveNext()) {
            Object obj = objEnum.get_Current();
            Console.WriteLine("\t[{0}]:\t{1}",(Int32)i++, obj);
        }
        Console.WriteLine();
    } //PrintIndexAndValues
} //SamplesArrayList
 
/* 
This code produces the following output.
The ArrayList initially contains the following values:
        [0]:    The
        [1]:    quick
        [2]:    brown
        [3]:    fox
        [4]:    jumps
        [5]:    over
        [6]:    the
        [7]:    lazy
        [8]:    dog

After sorting with the default comparer:
        [0]:    brown
        [1]:    dog
        [2]:    fox
        [3]:    jumps
        [4]:    lazy
        [5]:    over
        [6]:    quick
        [7]:    the
        [8]:    The

After sorting with the reverse case-insensitive comparer:
        [0]:    the
        [1]:    The
        [2]:    quick
        [3]:    over
        [4]:    lazy
        [5]:    jumps
        [6]:    fox
        [7]:    dog
        [8]:    brown 
*/

Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

XNA Framework

Supported in: 1.0

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