IComparable IComparable IComparable IComparable Interface

定義

定義通用的型別特定比較方法,實值型別 (Value Type) 或類別 (Class) 會實作這個方法,以排列或排序其執行個體。Defines a generalized type-specific comparison method that a value type or class implements to order or sort its instances.

public interface class IComparable
[System.Runtime.InteropServices.ComVisible(true)]
public interface IComparable
type IComparable = interface
Public Interface IComparable
衍生
屬性

範例

下列範例說明實作IComparable和必要CompareTo方法。The following example illustrates the implementation of IComparable and the requisite CompareTo method.

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
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

備註

實作這個介面是由可以排列或排序其值的型別。This interface is implemented by types whose values can be ordered or sorted. 它需要實作的類型會定義單一方法CompareTo(Object),指出是否目前的執行個體在排序次序的位置之前,之後,或是與相同類型的第二個物件相同。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. 執行個體IComparable實作會自動呼叫方法這類Array.SortArrayList.SortThe instance's IComparable implementation is called automatically by methods such as Array.Sort and ArrayList.Sort.

實作CompareTo(Object)方法必須傳回Int32具有三個值之一下, 表所示。The implementation of the CompareTo(Object) method must return an Int32 that has one of three values, as shown in the following table.

Value 意義Meaning
小於零Less than zero 目前的執行個體之前所指定的物件CompareTo在排序次序的方法。The current instance precedes the object specified by the CompareTo method in the sort order.
Zero 此目前執行個體,就會發生在相同位置中的排序次序所指定的物件為CompareTo方法。This current instance occurs in the same position in the sort order as the object specified by the CompareTo method.
大於零Greater than zero 此目前執行個體所指定的物件會遵循CompareTo在排序次序的方法。This current instance follows the object specified by the CompareTo method in the sort order.

所有數字類型 (例如Int32Double) 實作IComparable,就像一樣StringChar,和DateTimeAll numeric types (such as Int32 and Double) implement IComparable, as do String, Char, and DateTime. 自訂類型應該也會提供其自己實作的IComparable排列或排序的物件執行個體。Custom types should also provide their own implementation of IComparable to enable object instances to be ordered or sorted.

方法

CompareTo(Object) CompareTo(Object) CompareTo(Object) CompareTo(Object)

將目前的執行個體與相同型別的另一個物件相比較,並傳回整數,這個整數表示目前的執行個體在排序次序中,位於另一個物件之前、之後或相同位置。Compares the current instance with another object of the same type and returns an integer that indicates whether the current instance precedes, follows, or occurs in the same position in the sort order as the other object.

適用於