IComparer Interface
Assembly: mscorlib (in mscorlib.dll)
This interface is used in conjunction with the Array.Sort and Array.BinarySearch methods. It provides a way to customize the sort order of a collection.
The default implementation of this interface is the Comparer class. For the generic version of this interface, see System.Collections.Generic.IComparer.
The following code example demonstrates the use of the IComparer interface to sort an ArrayList object. In this example, the IComparer interface is implemented using the CaseInsensitiveComparer class to reverse the order of the contents of the ArrayList.
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.