# IStructuralComparable.CompareTo(Object, IComparer) 方法

## 定義

``````public:
int CompareTo(System::Object ^ other, System::Collections::IComparer ^ comparer);``````
``public int CompareTo (object other, System.Collections.IComparer comparer);``
``public int CompareTo (object? other, System.Collections.IComparer comparer);``
``abstract member CompareTo : obj * System.Collections.IComparer -> int``
``Public Function CompareTo (other As Object, comparer As IComparer) As Integer``

other
Object

comparer
IComparer

#### 傳回

- 若小於 0，目前的執行個體在 `other` 之前。
- 若等於 0，目前的執行個體與 `other` 相等。
- 若大於 0，目前的執行個體在 `other` 之後。

-1 目前的執行個體在 `other` 之前。
0 目前的執行個體與 `other` 相等。
1 目前的執行個體在 `other` 之後。

## 範例

``````using System;
using System.Collections;
using System.Collections.Generic;

public class PopulationComparer<T1, T2, T3, T4, T5, T6> : IComparer
{
private int itemPosition;
private int multiplier = -1;

public PopulationComparer(int component) : this(component, true)
{ }

public PopulationComparer(int component, bool descending)
{
if (! descending) multiplier = 1;

if (component <= 0 || component > 6)
throw new ArgumentException("The component argument is out of range.");

itemPosition = component;
}

public int Compare(object x, object y)
{
var tX = x as Tuple<T1, T2, T3, T4, T5, T6>;
if (tX == null)
{
return 0;
}
else
{
var tY = y as Tuple<T1, T2, T3, T4, T5, T6>;
switch (itemPosition)
{
case 1:
return Comparer<T1>.Default.Compare(tX.Item1, tY.Item1) * multiplier;
case 2:
return Comparer<T2>.Default.Compare(tX.Item2, tY.Item2) * multiplier;
case 3:
return Comparer<T3>.Default.Compare(tX.Item3, tY.Item3) * multiplier;
case 4:
return Comparer<T4>.Default.Compare(tX.Item4, tY.Item4) * multiplier;
case 5:
return Comparer<T5>.Default.Compare(tX.Item5, tY.Item5) * multiplier;
case 6:
return Comparer<T6>.Default.Compare(tX.Item6, tY.Item6) * multiplier;
default:
return Comparer<T1>.Default.Compare(tX.Item1, tY.Item1) * multiplier;
}
}
}
}

public class Example
{
public static void Main()
{
// Create array of sextuple with population data for three U.S.
// cities, 1960-2000.
Tuple<string, int, int, int, int, int>[] cities =
{ Tuple.Create("Los Angeles", 2479015, 2816061, 2966850, 3485398, 3694820),
Tuple.Create("New York", 7781984, 7894862, 7071639, 7322564, 8008278),
Tuple.Create("Chicago", 3550904, 3366957, 3005072, 2783726, 2896016) };

// Display array in unsorted order.
Console.WriteLine("In unsorted order:");
foreach (var city in cities)
Console.WriteLine(city.ToString());
Console.WriteLine();

Array.Sort(cities, new PopulationComparer<string, int, int, int, int, int>(3));

// Display array in sorted order.
Console.WriteLine("Sorted by population in 1970:");
foreach (var city in cities)
Console.WriteLine(city.ToString());
Console.WriteLine();

Array.Sort(cities, new PopulationComparer<string, int, int, int, int, int>(6));

// Display array in sorted order.
Console.WriteLine("Sorted by population in 2000:");
foreach (var city in cities)
Console.WriteLine(city.ToString());
}
}
// The example displays the following output:
//    In unsorted order:
//    (Los Angeles, 2479015, 2816061, 2966850, 3485398, 3694820)
//    (New York, 7781984, 7894862, 7071639, 7322564, 8008278)
//    (Chicago, 3550904, 3366957, 3005072, 2783726, 2896016)
//
//    Sorted by population in 1970:
//    (New York, 7781984, 7894862, 7071639, 7322564, 8008278)
//    (Chicago, 3550904, 3366957, 3005072, 2783726, 2896016)
//    (Los Angeles, 2479015, 2816061, 2966850, 3485398, 3694820)
//
//    Sorted by population in 2000:
//    (New York, 7781984, 7894862, 7071639, 7322564, 8008278)
//    (Los Angeles, 2479015, 2816061, 2966850, 3485398, 3694820)
//    (Chicago, 3550904, 3366957, 3005072, 2783726, 2896016)
``````
``````Imports System.Collections
Imports System.Collections.Generic

Public Class PopulationComparer(Of T1, T2, T3, T4, T5, T6) : 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 > 6 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 = TryCast(x, Tuple(Of T1, T2, T3, T4, T5, T6))
If tX Is Nothing Then
Return 0
Else
Dim tY = DirectCast(y, Tuple(Of T1, T2, T3, T4, T5, T6))
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
' This should never happen.
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, 1960-2000.
Dim cities() =
{ Tuple.Create("Los Angeles", 2479015, 2816061, 2966850, 3485398, 3694820),
Tuple.Create("New York", 7781984, 7894862, 7071639, 7322564, 8008278),
Tuple.Create("Chicago", 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)(3))

' Display array in sorted order.
Console.WriteLine("Sorted by population in 1970:")
For Each city In cities
Console.WriteLine(city.ToString())
Next
Console.WriteLine()

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

' Display array in sorted order.
Console.WriteLine("Sorted by population in 2000:")
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, 2479015, 2816061, 2966850, 3485398, 3694820)
'    (New York, 7781984, 7894862, 7071639, 7322564, 8008278)
'    (Chicago, 3550904, 3366957, 3005072, 2783726, 2896016)
'
'    Sorted by population in 1970:
'    (New York, 7781984, 7894862, 7071639, 7322564, 8008278)
'    (Chicago, 3550904, 3366957, 3005072, 2783726, 2896016)
'    (Los Angeles, 2479015, 2816061, 2966850, 3485398, 3694820)
'
'    Sorted by population in 2000:
'    (New York, 7781984, 7894862, 7071639, 7322564, 8008278)
'    (Los Angeles, 2479015, 2816061, 2966850, 3485398, 3694820)
'    (Chicago, 3550904, 3366957, 3005072, 2783726, 2896016)
``````