IComparable.CompareTo(Object) 方法

定義

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.

public:
 int CompareTo(System::Object ^ obj);
public int CompareTo (object obj);
abstract member CompareTo : obj -> int
Public Function CompareTo (obj As Object) As Integer

參數

obj
Object

與這個執行個體相互比較的物件。An object to compare with this instance.

傳回

Int32

值,表示所比較之物件的相對順序。A value that indicates the relative order of the objects being compared. 傳回值具有這些意義:The return value has these meanings:

Value 意義Meaning
小於零Less than zero 這個執行個體在排序次序中會在 obj 之前。This instance precedes obj in the sort order.
Zero 這個執行個體在排序次序中的位置和 obj 相同。This instance occurs in the same position in the sort order as obj.
大於零Greater than zero 這個執行個體在排序順序中會跟在 obj 之後。This instance follows obj in the sort order.

例外狀況

obj 與這個執行個體的型別不同。obj is not the same type as this instance.

範例

下列範例說明 CompareTo 如何使用來比較 Temperature 與另一個物件執行的物件 IComparableThe following example illustrates the use of CompareTo to compare a Temperature object implementing IComparable with another object. Temperature CompareTo 只要將呼叫包裝到方法,就可以執行此物件 Int32.CompareToThe Temperature object implements CompareTo by simply wrapping a call to the Int32.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

CompareTo方法是由可以排序或排序值的型別所執行。The CompareTo method is implemented by types whose values can be ordered or sorted. 它是由非泛型集合物件(例如)的方法自動呼叫, Array.Sort 以排序陣列的每個成員。It is called automatically by methods of non-generic collection objects, such as Array.Sort, to order each member of the array. 如果自訂類別或結構未執行 IComparable ,則無法將其成員排序,且排序作業可以擲回 InvalidOperationExceptionIf a custom class or structure does not implement IComparable, its members cannot be ordered and the sort operation can throw an InvalidOperationException.

這個方法只是定義,而且必須由特定類別或實值型別實作為效果。This method is only a definition and must be implemented by a specific class or value type to have effect. 傳回值區段中所指定之比較的意義 ( "在" 之前 "、" 發生在與 "相同的位置,而「遵循」 ) 取決於特定的執行。The meaning of the comparisons specified in the Return Value section ("precedes", "occurs in the same position as", and "follows") depends on the particular implementation.

根據定義,任何物件的比較都會大於 (或之後) null ,而兩個 null 參考比較等於彼此。By definition, any object compares greater than (or follows) null, and two null references compare equal to each other.

參數的 obj 類型必須與實此介面的類別或實值型別相同,否則會擲回 ArgumentExceptionThe parameter, obj, must be the same type as the class or value type that implements this interface; otherwise, an ArgumentException is thrown.

給實施者的注意事項

針對物件 A、B 和 C,下列條件必須為 true:For objects A, B and C, the following must be true: CompareTo () 必須傳回零。A.CompareTo(A) must return zero.

如果 . CompareTo (B) 傳回零,則 CompareTo () 必須傳回零。If A.CompareTo(B) returns zero, then B.CompareTo(A) must return zero.

如果 . CompareTo (B) 會傳回零,而 CompareTo (C) 會傳回零,則 CompareTo (C) 必須傳回零。If A.CompareTo(B) returns zero and B.CompareTo(C) returns zero, then A.CompareTo(C) must return zero.

如果 . CompareTo (B) 傳回零以外的值,則 b. CompareTo () 必須傳回相反正負號的值。If A.CompareTo(B) returns a value other than zero, then B.CompareTo(A) must return a value of the opposite sign.

如果 . CompareTo (B) x 會傳回不等於零的值,而且 b. CompareTo (C) 會傳回 y 相同正負號的值 x ,則 CompareTo (C) 必須傳回與和相同的正負號值 x yIf A.CompareTo(B) returns a value x not equal to zero, and B.CompareTo(C) returns a value y of the same sign as x, then A.CompareTo(C) must return a value of the same sign as x and y.

給呼叫者的注意事項

CompareTo(Object) 可以使用方法來判斷類別實例的順序。Use the CompareTo(Object) method to determine the ordering of instances of a class.

適用於

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