Tuple(Of T1, T2, T3, T4, T5, T6, T7).IStructuralComparable.CompareTo Method (Object, IComparer)

 

Compares the current Tuple(Of T1, T2, T3, T4, T5, T6, T7) 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

Parameters

other
Type: System.Object

An object to compare with the current instance.

comparer
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.

Value

Description

A negative integer

This instance precedes other.

Zero

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

A positive integer

This instance follows other.

This member is an explicit interface implementation. It can be used only when the Tuple(Of T1, T2, T3, T4, T5, T6, T7) instance is cast to an IStructuralComparable interface.

This method lets you define customized comparisons of Tuple(Of T1, T2, T3, T4, T5, T6, T7) objects. For example, you can use this method to order Tuple(Of T1, T2, T3, T4, T5, T6, T7) objects based on the value of a specific component.

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.

System_CAPS_cautionCaution

The 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 IStructuralEquatable.Equals method.

The following example creates an array of Tuple(Of T1, T2, T3, T4, T5, T6, T7) objects that contains population data for three U.S. cities from 1950 to 2000. The septuple's first component is the city name. The remaining five components represent the population at 10-year intervals from 1950 to 2000.

The PopulationComparer class provides an IComparer implementation that allows the array of septuples to be sorted by any one of its components. Two values are provided to the PopulationComparer class in its constructor: The position of the component that defines the sort order, and a Boolean value that indicates whether the tuple objects should be sorted in ascending or descending order.

The example then displays the elements in the array in unsorted order, sorts them by the third component (the population in 1960) and displays them, and then sorts them by the sixth component (the population in 1990) and displays them.

Imports System.Collections
Imports System.Collections.Generic

Public Class PopulationComparer(Of T1, T2, T3, T4, T5, T6, T7) : Implements IComparer
   Private itemPosition As Integer
   Private multiplier As Integer = -1

   Public Sub New(component As Integer)
      Me.New(component, True)
   End Sub

   Public Sub New(component As Integer, descending As Boolean)
      If Not descending Then multiplier = 1

      If component <= 0 Or component > 7 Then 
         Throw New ArgumentException("The component argument is out of range.")
      End If
      itemPosition = component
   End Sub 

   Public Function Compare(x As Object, y As Object) As Integer _
                   Implements IComparer.Compare

      Dim tX As Tuple(Of T1, T2, T3, T4, T5, T6, T7) = TryCast(x, Tuple(Of T1, T2, T3, T4, T5, T6, T7))
      If tX Is Nothing Then
         Return 0
      Else
         Dim tY As Tuple(Of T1, T2, T3, T4, T5, T6, T7) = DirectCast(y, Tuple(Of T1, T2, T3, T4, T5, T6, T7))
         Select Case itemPosition
            Case 1
               Return Comparer(Of T1).Default.Compare(tX.Item1, tY.Item1) * multiplier
            Case 2
               Return Comparer(Of T2).Default.Compare(tX.Item2, tY.Item2) * multiplier
            Case 3
               Return Comparer(Of T3).Default.Compare(tX.Item3, tY.Item3) * multiplier
            Case 4
               Return Comparer(Of T4).Default.Compare(tX.Item4, tY.Item4) * multiplier
            Case 5
               Return Comparer(Of T5).Default.Compare(tX.Item5, tY.Item5) * multiplier
            Case 6
               Return Comparer(Of T6).Default.Compare(tX.Item6, tY.Item6) * multiplier
            Case 7
               Return Comparer(Of T7).Default.Compare(tX.Item7, tY.Item7) * multiplier
            ' This should never be reached.
            Case Else
               Return 0
         End Select      
      End If
   End Function
End Class

Module Example
   Public Sub Main()
      ' Create array of sextuple with population data for three U.S. 
      ' cities, 1950-2000.
      Dim cities() = 
          { Tuple.Create("Los Angeles", 1970358, 2479015, 2816061, 2966850, 3485398, 3694820),
            Tuple.Create("New York", 7891957, 7781984, 7894862, 7071639, 7322564, 8008278),  
            Tuple.Create("Chicago", 3620962, 3550904, 3366957, 3005072, 2783726, 2896016) } 

      ' Display array in unsorted order.
      Console.WriteLine("In unsorted order:")
      For Each city In cities
         Console.WriteLine(city.ToString())
      Next
      Console.WriteLine()

      Array.Sort(cities, New PopulationComparer(Of String, Integer, Integer, Integer, Integer, Integer, Integer)(3)) 

      ' Display array in sorted order.
      Console.WriteLine("Sorted by population in 1960:")
      For Each city In cities
         Console.WriteLine(city.ToString())
      Next
      Console.WriteLine()

      Array.Sort(cities, New PopulationComparer(Of String, Integer, Integer, Integer, Integer, Integer, Integer)(6))

      ' Display array in sorted order.
      Console.WriteLine("Sorted by population in 1990:")
      For Each city In cities
         Console.WriteLine(city.ToString())
      Next
   End Sub
End Module
' The example displays the following output:
'    In unsorted order:
'    (Los Angeles, 1970358, 2479015, 2816061, 2966850, 3485398, 3694820)
'    (New York, 7891957, 7781984, 7894862, 7071639, 7322564, 8008278)
'    (Chicago, 3620962, 3550904, 3366957, 3005072, 2783726, 2896016)
'    
'    Sorted by population in 1960:
'    (New York, 7891957, 7781984, 7894862, 7071639, 7322564, 8008278)
'    (Chicago, 3620962, 3550904, 3366957, 3005072, 2783726, 2896016)
'    (Los Angeles, 1970358, 2479015, 2816061, 2966850, 3485398, 3694820)
'    
'    Sorted by population in 1990:
'    (New York, 7891957, 7781984, 7894862, 7071639, 7322564, 8008278)
'    (Los Angeles, 1970358, 2479015, 2816061, 2966850, 3485398, 3694820)
'    (Chicago, 3620962, 3550904, 3366957, 3005072, 2783726, 2896016)

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