Defines a generalized type-specific comparison method that a value type or class implements to order or sort its instances.
Assembly: mscorlib (in mscorlib.dll)
Thetype exposes the following members.
This interface is implemented by types whose values can be ordered or sorted. It requires that implementing types define a single method, CompareTo(Object), that indicates whether the position of the current instance in the sort order is before, after, or the same as a second object of the same type. The instance's implementation is called automatically by methods such as Array.Sort and ArrayList.Sort.
Less than zero
The current instance precedes the object specified by the CompareTo method in the sort order.
This current instance occurs in the same position in the sort order as the object specified by the CompareTo method.
Greater than zero
This current instance follows the object specified by the CompareTo method in the sort order.
All numeric types (such as Int32 and Double) implement , as do String, Char, and DateTime. Custom types should also provide their own implementation of to enable object instances to be ordered or sorted.
The following example illustrates the implementation of and the requisite CompareTo method.
Imports System.Collections Public Class Temperature Implements IComparable ' The temperature value Protected temperatureF As Double Public Overloads Function CompareTo(ByVal obj As Object) As Integer _ Implements IComparable.CompareTo If obj Is Nothing Then Return 1 Dim otherTemperature As Temperature = TryCast(obj, Temperature) If otherTemperature IsNot Nothing Then Return Me.temperatureF.CompareTo(otherTemperature.temperatureF) Else Throw New ArgumentException("Object is not a Temperature") End If End Function Public Property Fahrenheit() As Double Get Return temperatureF End Get Set(ByVal Value As Double) Me.temperatureF = Value End Set End Property Public Property Celsius() As Double Get Return (temperatureF - 32) * (5/9) End Get Set(ByVal Value As Double) Me.temperatureF = (Value * 9/5) + 32 End Set End Property End Class Public Module CompareTemperatures Public Sub Main() Dim temperatures As New ArrayList ' Initialize random number generator. Dim rnd As New Random() ' Generate 10 temperatures between 0 and 100 randomly. For ctr As Integer = 1 To 10 Dim degrees As Integer = rnd.Next(0, 100) Dim temp As New Temperature temp.Fahrenheit = degrees temperatures.Add(temp) Next ' Sort ArrayList. temperatures.Sort() For Each temp As Temperature In temperatures Console.WriteLine(temp.Fahrenheit) Next End Sub End Module ' The example displays the following output to the console (individual ' values may vary because they are randomly generated): ' 2 ' 7 ' 16 ' 17 ' 31 ' 37 ' 58 ' 66 ' 72 ' 95