IComparer(T).Compare Method (System.Collections.Generic)

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.NET Framework Class Library
IComparer<T>.Compare Method

Updated: June 2010

Compares two objects and returns a value indicating whether one is less than, equal to, or greater than the other.

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

Visual Basic
Function Compare ( _
	x As T, _
	y As T _
) As Integer
C#
int Compare(
	T x,
	T y
)
Visual C++
int Compare(
	T x, 
	T y
)
F#
abstract Compare : 
        x:'T * 
        y:'T -> int 

Parameters

x
Type: T
The first object to compare.
y
Type: T
The second object to compare.

Return Value

Type: System.Int32
A signed integer that indicates the relative values of x and y, as shown in the following table.

Value

Meaning

Less than zero

x is less than y.

Zero

x equals y.

Greater than zero

x is greater than y.

Remarks

Implement this method to provide a customized sort order comparison for type T.

Comparing null with any reference type is allowed and does not generate an exception. A null reference is considered to be less than any reference that is not null.

Examples

The following example implements the IComparer<T> interface to compare objects of type Box according to their dimensions. This example is part of a larger example provided for the Comparer<T> class.

Visual Basic

' This class is not demonstrated in the Main method
' and is provided only to show how to implement
' the interface. It is recommended to derive
' from Comparer<T> instead of implementing IComparer<T>.
Public Class BoxComp
	Implements IComparer(Of Box)
	' Compares by Height, Length, and Width.
    Public Function Compare(ByVal x As Box, ByVal y As Box) As Integer Implements _
                                                IComparer(Of Box).Compare
        If x.Height.CompareTo(y.Height) <> 0 Then
            Return x.Height.CompareTo(y.Height)
        ElseIf x.Length.CompareTo(y.Length) <> 0 Then
            Return x.Length.CompareTo(y.Length)
        ElseIf x.Width.CompareTo(y.Width) <> 0 Then
            Return x.Width.CompareTo(y.Width)
        Else
            Return 0
        End If
    End Function
End Class


C#

// This class is not demonstrated in the Main method
// and is provided only to show how to implement
// the interface. It is recommended to derive
// from Comparer<T> instead of implementing IComparer<T>.
public class BoxComp : IComparer<Box>
{
    // Compares by Height, Length, and Width.
    public int Compare(Box x, Box y)
    {
        if (x.Height.CompareTo(y.Height) != 0)
        {
            return x.Height.CompareTo(y.Height);
        }
        else if (x.Length.CompareTo(y.Length) != 0)
        {
            return x.Length.CompareTo(y.Length);
        }
        else if (x.Width.CompareTo(y.Width) != 0)
        {
            return x.Width.CompareTo(y.Width);
        }
        else
        {
            return 0;
        }
    }
}


Version Information

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library
Platforms

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.
See Also

Reference

Change History

Date

History

Reason

June 2010

Added example.

Information enhancement.