Tuple(Of T1, T2, T3).IStructuralComparable.CompareTo Method (Object, IComparer)


Compares the current Tuple(Of T1, T2, T3) object to a specified object by using a specified comparer, and returns an integer that indicates whether the current object is before, after, or in the same position as the specified object in the sort order.

Namespace:   System
Assembly:  mscorlib (in mscorlib.dll)

Private Function CompareTo (
	other As Object,
	comparer As IComparer
) As Integer
	Implements IStructuralComparable.CompareTo


Type: System.Object

An object to compare with the current instance.

Type: System.Collections.IComparer

An object that provides custom rules for comparison.

Return Value

Type: System.Int32

A signed integer that indicates the relative position of this instance and other in the sort order, as shown in the following table.



A negative integer

This instance precedes other.


This instance and other have the same position in the sort order.

A positive integer

This instance follows other.

Exception Condition

other is not a Tuple(Of T1, T2, T3) object.

This member is an explicit interface member implementation. It can be used only when the Tuple(Of T1, T2, T3) instance is cast to an IStructuralComparable interface.

Although this method can be called directly, it is most commonly called by collection sorting methods that include IComparer parameters to order the members of a collection. For example, it is called by the Array.Sort(Array, IComparer) method and the Add method of a SortedList object that is instantiated by using the SortedList.SortedList(IComparer) constructor.


The Tuple(Of T1, T2, T3).IStructuralComparable.CompareTo method is intended for use in sorting operations. It should not be used when the primary purpose of a comparison is to determine whether two objects are equal. To determine whether two objects are equal, call the Tuple(Of T1, T2, T3).IStructuralEquatable.Equals method.

The following example creates an array of Tuple(Of T1, T2, T3) objects that consist of a student's name, mean test score, and number of tests. It displays the component of each tuple in the array in unsorted order, sorts the array, and then calls ToString to display the value of each tuple in sorted order. To sort the array, the example defines a generic ScoreComparer class that implements the IComparer interface and sorts the Tuple(Of T1, T2, T3) objects in ascending order by the value of their second component rather than their first component. Note that the example does not directly call the Tuple(Of T1, T2, T3).IStructuralComparable.CompareTo method. This method is called implicitly by the Array.Sort(Array, IComparer) method for each element in the array.

Imports System.Collections
Imports System.Collections.Generic

Public Class ScoreComparer(Of T1, T2, T3) : Implements IComparer
   Public Function Compare(x As Object, y As Object) As Integer _
                   Implements IComparer.Compare
      Dim tX As Tuple(Of T1, T2, T3) = TryCast(x, Tuple(Of T1, T2, T3))
      If tX Is Nothing Then
         Return 0
         Dim tY As Tuple(Of T1, T2, T3) = DirectCast(y, Tuple(Of T1, T2, T3))
         Return Comparer(Of T2).Default.Compare(tx.Item2, tY.Item2)             
      End If
   End Function
End Class

Module Example
   Public Sub Main()
      Dim scores() = 
                 { Tuple.Create("Jack", 78.8, 8),
                   Tuple.Create("Abbey", 92.1, 9), 
                   Tuple.Create("Dave", 88.3, 9),
                   Tuple.Create("Sam", 91.7, 8), 
                   Tuple.Create("Ed", 71.2, 5),
                   Tuple.Create("Penelope", 82.9, 8),
                   Tuple.Create("Linda", 99.0, 9),
                   Tuple.Create("Judith", 84.3, 9) }

      Console.WriteLine("The values in unsorted order:")
      For Each score In scores

      Array.Sort(scores, New ScoreComparer(Of String, Double, Integer)())

      Console.WriteLine("The values in sorted order:")
      For Each score In scores
   End Sub
End Module
' The example displays the following output;
'       The values in unsorted order:
'       (Jack, 78.8, 8)
'       (Abbey, 92.1, 9)
'       (Dave, 88.3, 9)
'       (Sam, 91.7, 8)
'       (Ed, 71.2, 5)
'       (Penelope, 82.9, 8)
'       (Linda, 99, 9)
'       (Judith, 84.3, 9)
'       The values in sorted order:
'       (Ed, 71.2, 5)
'       (Jack, 78.8, 8)
'       (Penelope, 82.9, 8)
'       (Judith, 84.3, 9)
'       (Dave, 88.3, 9)
'       (Sam, 91.7, 8)
'       (Abbey, 92.1, 9)
'       (Linda, 99, 9)

Universal Windows Platform
Available since 8
.NET Framework
Available since 4.0
Portable Class Library
Supported in: portable .NET platforms
Available since 4.0
Windows Phone Silverlight
Available since 8.0
Windows Phone
Available since 8.1
Return to top