IComparable.CompareTo(Object) 方法

定义

命名空间:

System

程序集:

System.Runtime.dll

将当前实例与同一类型的另一个对象进行比较，并返回一个整数，该整数指示当前实例在排序顺序中是否与另一个对象位于同一位置。

public:
 int CompareTo(System::Object ^ obj);

public int CompareTo (object? obj);

abstract member CompareTo : obj -> int

Public Function CompareTo (obj As Object) As Integer

参数

obj

Object

要与此实例进行比较的对象。

返回

Int32

一个值，该值指示所比较对象的相对顺序。 返回值具有以下含义：

价值	意义
小于零	此实例在排序顺序 obj 之前。
零	此实例的排序顺序与 obj相同。
大于零	此实例按排序顺序遵循 obj。

例外

ArgumentException

obj 的类型与此实例不同。

示例

下面的示例演示如何使用 CompareTo 将实现 IComparable 的 Temperature 对象与其他对象进行比较。 Temperature 对象只需包装对 Int32.CompareTo 方法的调用即可实现 CompareTo。

using namespace System;
using namespace System::Collections;

public ref class Temperature: public IComparable {
   /// <summary>
   /// IComparable.CompareTo implementation.
   /// </summary>
protected:
   // The value holder
   Double m_value;

public:
   virtual Int32 CompareTo( Object^ obj ) {
   
      if (obj == nullptr) return 1;
      
      if ( obj->GetType() == Temperature::typeid ) {
         Temperature^ temp = dynamic_cast<Temperature^>(obj);

         return m_value.CompareTo( temp->m_value );
      }
      throw gcnew ArgumentException(  "object is not a Temperature" );
   }

   property Double Value {
      Double get() {
         return m_value;
      }
      void set( Double value ) {
         m_value = value;
      }
   }

   property Double Celsius  {
      Double get() {
         return (m_value - 32) / 1.8;
      }
      void set( Double value ) {
         m_value = (value * 1.8) + 32;
      }
   }
};

int main()
{
   ArrayList^ temperatures = gcnew ArrayList;
   // Initialize random number generator.
   Random^ rnd = gcnew Random;

   // Generate 10 temperatures between 0 and 100 randomly.
   for (int ctr = 1; ctr <= 10; ctr++)
   {
      int degrees = rnd->Next(0, 100);
      Temperature^ temp = gcnew Temperature;
      temp->Value = degrees;
      temperatures->Add(temp);
   }

   // Sort ArrayList.
   temperatures->Sort();
      
   for each (Temperature^ temp in temperatures)
      Console::WriteLine(temp->Value);
   return 0;
}
// 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

using System;
using System.Collections;

public class Temperature : IComparable
{
    // The temperature value
    protected double temperatureF;

    public int CompareTo(object obj) {
        if (obj == null) return 1;

        Temperature otherTemperature = obj as Temperature;
        if (otherTemperature != null)
            return this.temperatureF.CompareTo(otherTemperature.temperatureF);
        else
           throw new ArgumentException("Object is not a Temperature");
    }

    public double Fahrenheit
    {
        get
        {
            return this.temperatureF;
        }
        set 
        {
            this.temperatureF = value;
        }
    }

    public double Celsius
    {
        get
        {
            return (this.temperatureF - 32) * (5.0/9);
        }
        set
        {
            this.temperatureF = (value * 9.0/5) + 32;
        }
    }
}

public class CompareTemperatures
{
   public static void Main()
   {
      ArrayList temperatures = new ArrayList();
      // Initialize random number generator.
      Random rnd = new Random();

      // Generate 10 temperatures between 0 and 100 randomly.
      for (int ctr = 1; ctr <= 10; ctr++)
      {
         int degrees = rnd.Next(0, 100);
         Temperature temp = new Temperature();
         temp.Fahrenheit = degrees;
         temperatures.Add(temp);
      }

      // Sort ArrayList.
      temperatures.Sort();

      foreach (Temperature temp in temperatures)
         Console.WriteLine(temp.Fahrenheit);
   }
}
// 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

open System
open System.Collections

type Temperature() =
    // The temperature value
    let mutable temperatureF = 0.

    interface IComparable with
        member _.CompareTo(obj) =
            match obj with 
            | null -> 1
            | :? Temperature as other -> 
                temperatureF.CompareTo other.Fahrenheit
            | _ ->
                invalidArg (nameof obj) "Object is not a Temperature"

    member _.Fahrenheit 
        with get () =
            temperatureF
        and set (value) = 
            temperatureF <- value

    member _.Celsius
        with get () =
            (temperatureF - 32.) * (5. / 9.)
        and set (value) =
            temperatureF <- (value * 9. / 5.) + 32.

let temperatures = ResizeArray()

// Initialize random number generator.
let rnd = Random()

// Generate 10 temperatures between 0 and 100 randomly.
for _ = 1 to 10 do
    let degrees = rnd.Next(0, 100)
    let temp = Temperature(Fahrenheit=degrees)
    temperatures.Add temp

// Sort ResizeArray.
temperatures.Sort()

for temp in temperatures do
    printfn $"{temp.Fahrenheit}"

// 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

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

注解

CompareTo 方法由可以排序或排序其值的类型实现。 它由非泛型集合对象（如 Array.Sort）的方法自动调用，以便对数组的每个成员进行排序。 如果自定义类或结构未实现 IComparable，则无法对成员进行排序，排序操作可以引发 InvalidOperationException。

此方法只是一个定义，必须由特定的类或值类型实现才能生效。 返回值节中指定的比较的含义（“前面”、“发生于同一位置”和“follows”）取决于特定实现。

根据定义，任何对象都会比较大于（或关注）null，两个 null 引用相互比较相等。

参数 obj必须与实现此接口的类或值类型相同;否则，将引发 ArgumentException。

实施者说明

对于对象 A、B 和 C，必须执行以下操作：

A.CompareTo(A) 必须返回零。

如果 A.CompareTo(B) 返回零，则 B.CompareTo(A) 必须返回零。

如果 A.CompareTo(B) 返回零并且 B.CompareTo(C) 返回零，则 A.CompareTo(C) 必须返回零。

如果 A.CompareTo(B) 返回除零以外的值，则 B.CompareTo(A) 必须返回相反符号的值。

如果 A.CompareTo(B) 返回值“x”不等于零，并且 B.CompareTo(C) 返回与“x”相同的符号的值“y”，则 A.CompareTo(C) 必须返回与“x”和“y”相同的符号的值。

调用方说明

使用 CompareTo(Object) 方法确定类实例的排序。

另请参阅

• Object