Exposes a method that compares two objects.
Namespace: System.Collections
Assembly: mscorlib (in mscorlib.dll)
Visual Basic (Declaration)
<ComVisibleAttribute(True)> _
Public Interface IComparer
Dim instance As IComparer
[ComVisibleAttribute(true)]
public interface IComparer
[ComVisibleAttribute(true)]
public interface class IComparer
/** @attribute ComVisibleAttribute(true) */
public interface IComparer
ComVisibleAttribute(true)
public interface IComparer
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
using System;
using System.Collections;
public class SamplesArrayList {
public class myReverserClass : IComparer {
// Calls CaseInsensitiveComparer.Compare with the parameters reversed.
int IComparer.Compare( Object x, Object y ) {
return( (new CaseInsensitiveComparer()).Compare( y, x ) );
}
}
public static void Main() {
// 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 );
}
public static void PrintIndexAndValues( IEnumerable myList ) {
int i = 0;
foreach ( Object obj in myList )
Console.WriteLine( "\t[{0}]:\t{1}", i++, obj );
Console.WriteLine();
}
}
/*
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
*/
using namespace System;
using namespace System::Collections;
void PrintIndexAndValues( IEnumerable^ myList );
ref class myReverserClass: public IComparer
{
private:
// Calls CaseInsensitiveComparer.Compare with the parameters reversed.
virtual int Compare( Object^ x, Object^ y ) = IComparer::Compare
{
return ((gcnew CaseInsensitiveComparer)->Compare( y, x ));
}
};
int main()
{
// Creates and initializes a new ArrayList.
ArrayList^ myAL = gcnew 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 = gcnew myReverserClass;
myAL->Sort( myComparer );
Console::WriteLine( "After sorting with the reverse case-insensitive comparer:" );
PrintIndexAndValues( myAL );
}
void PrintIndexAndValues( IEnumerable^ myList )
{
int i = 0;
IEnumerator^ myEnum = myList->GetEnumerator();
while ( myEnum->MoveNext() )
{
Object^ obj = safe_cast<Object^>(myEnum->Current);
Console::WriteLine( "\t[{0}]:\t{1}", i++, obj );
}
Console::WriteLine();
}
/*
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