Comparer<T>.Compare(T, T) Method


When overridden in a derived class, performs a comparison of two objects of the same type and returns a value indicating whether one object is less than, equal to, or greater than the other.

 abstract int Compare(T x, T y);
public abstract int Compare (T x, T y);
public abstract int Compare (T? x, T? y);
abstract member Compare : 'T * 'T -> int
Public MustOverride Function Compare (x As T, y As T) As Integer



The first object to compare.


The second object to compare.



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.



Type T does not implement either the IComparable<T> generic interface or the IComparable interface.


The following example defines a comparer of Box objects that can be used instead of the default comparer. This example is part of a larger example provided for the Comparer<T> class.

public class BoxLengthFirst : Comparer<Box>
    // Compares by Length, Height, and Width.
    public override int Compare(Box x, Box y)
        if (x.Length.CompareTo(y.Length) != 0)
            return x.Length.CompareTo(y.Length);
        else if (x.Height.CompareTo(y.Height) != 0)
            return x.Height.CompareTo(y.Height);
        else if (x.Width.CompareTo(y.Width) != 0)
            return x.Width.CompareTo(y.Width);
            return 0;
Public Class BoxLengthFirst
    Inherits Comparer(Of Box)
    ' Compares by Length, Height, and Width.
    Public Overrides Function Compare(ByVal x As Box, ByVal y As Box) As Integer
        If x.Length.CompareTo(y.Length) <> 0 Then
            Return x.Length.CompareTo(y.Length)
        ElseIf x.Height.CompareTo(y.Height) <> 0 Then
            Return x.Height.CompareTo(y.Height)
        ElseIf x.Width.CompareTo(y.Width) <> 0 Then
            Return x.Width.CompareTo(y.Width)
            Return 0
        End If
    End Function

End Class


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

Notes to Implementers

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.

For information on culture-specific comparisons, see the System.Globalization namespace and Globalization and Localization.

Applies to

See also