IComparable<T> IComparable<T> IComparable<T> IComparable<T> Interface

定義

定義通用的比較方法,實值型別或類別會實作這個方法,以建立特定類型的比較方法來排序其執行個體。Defines a generalized comparison method that a value type or class implements to create a type-specific comparison method for ordering or sorting its instances.

generic <typename T>
public interface class IComparable
public interface IComparable<in T>
type IComparable<'T> = interface
Public Interface IComparable(Of In T)

類型參數

T

要比較之物件的類型。The type of object to compare.

衍生

範例

下列程式碼範例說明如何實作IComparable<T>簡單Temperature物件。The following code example illustrates the implementation of IComparable<T> for a simple Temperature object. 此範例會建立SortedList<TKey,TValue>與字串集合Temperature物件索引鍵,並將溫度和字串的數個組加入至順序清單。The example creates a SortedList<TKey,TValue> collection of strings with Temperature object keys, and adds several pairs of temperatures and strings to the list out of sequence. 在呼叫Add方法中,SortedList<TKey,TValue>集合會使用IComparable<T>實作,以排序清單項目,然後會遞增溫度的順序顯示。In the call to the Add method, the SortedList<TKey,TValue> collection uses the IComparable<T> implementation to sort the list entries, which are then displayed in order of increasing temperature.

#using <System.dll>

using namespace System;
using namespace System::Collections::Generic;

public ref class Temperature: public IComparable<Temperature^> {

protected:
   // The underlying temperature value.
   Double m_value;

public:
   // Implement the generic CompareTo method with the Temperature class 
   // as the Type parameter. 
   virtual Int32 CompareTo( Temperature^ other ) {
   
      // If other is not a valid object reference, this instance 
      // is greater.
      if (other == nullptr) return 1;
      
      // The temperature comparison depends on the comparison of the
      // the underlying Double values. 
      return m_value.CompareTo( other->m_value );
   }

       // Define the is greater than operator.
    bool operator>=  (Temperature^ other)
    {
       return CompareTo(other) == 1;
    }
    
    // Define the is less than operator.
    bool operator<  (Temperature^ other)
    {
       return CompareTo(other) == -1;
    }
    
       // Define the is greater than or equal to operator.
    bool operator>  (Temperature^ other)
    {
       return CompareTo(other) >= 0;
    }
    
    // Define the is less than or equal to operator.
    bool operator<=  (Temperature^ other)
    {
       return CompareTo(other) <= 0;
    }

   property Double Celsius {
      Double get() {
         return m_value + 273.15;
      }
   }

   property Double Kelvin {
      Double get() {
         return m_value;
      }
      void set( Double value ) {
         if (value < 0)
            throw gcnew ArgumentException("Temperature cannot be less than absolute zero.");
         else
            m_value = value;
      }
   }

   Temperature(Double kelvins) {
      this->Kelvin = kelvins;
   }
};

int main() {
   SortedList<Temperature^, String^>^ temps = 
      gcnew SortedList<Temperature^, String^>();

   // Add entries to the sorted list, out of order.
   temps->Add(gcnew Temperature(2017.15), "Boiling point of Lead");
   temps->Add(gcnew Temperature(0), "Absolute zero");
   temps->Add(gcnew Temperature(273.15), "Freezing point of water");
   temps->Add(gcnew Temperature(5100.15), "Boiling point of Carbon");
   temps->Add(gcnew Temperature(373.15), "Boiling point of water");
   temps->Add(gcnew Temperature(600.65), "Melting point of Lead");

   for each( KeyValuePair<Temperature^, String^>^ kvp in temps )
   {
      Console::WriteLine("{0} is {1} degrees Celsius.", kvp->Value, kvp->Key->Celsius);
   }
}
/* The example displays the following output:
      Absolute zero is 273.15 degrees Celsius.
      Freezing point of water is 546.3 degrees Celsius.
      Boiling point of water is 646.3 degrees Celsius.
      Melting point of Lead is 873.8 degrees Celsius.
      Boiling point of Lead is 2290.3 degrees Celsius.
      Boiling point of Carbon is 5373.3 degrees Celsius.
*/
using System;
using System.Collections.Generic;

public class Temperature : IComparable<Temperature>
{
    // Implement the generic CompareTo method with the Temperature 
    // class as the Type parameter. 
    //
    public int CompareTo(Temperature other)
    {
        // If other is not a valid object reference, this instance is greater.
        if (other == null) return 1;
        
        // The temperature comparison depends on the comparison of 
        // the underlying Double values. 
        return m_value.CompareTo(other.m_value);
    }

    // Define the is greater than operator.
    public static bool operator >  (Temperature operand1, Temperature operand2)
    {
       return operand1.CompareTo(operand2) == 1;
    }
    
    // Define the is less than operator.
    public static bool operator <  (Temperature operand1, Temperature operand2)
    {
       return operand1.CompareTo(operand2) == -1;
    }

    // Define the is greater than or equal to operator.
    public static bool operator >=  (Temperature operand1, Temperature operand2)
    {
       return operand1.CompareTo(operand2) >= 0;
    }
    
    // Define the is less than or equal to operator.
    public static bool operator <=  (Temperature operand1, Temperature operand2)
    {
       return operand1.CompareTo(operand2) <= 0;
    }

    // The underlying temperature value.
    protected double m_value = 0.0;

    public double Celsius    
    {
        get
        {
            return m_value - 273.15;
        }
    }

    public double Kelvin    
    {
        get
        {
            return m_value;
        }
        set
        {
            if (value < 0.0)
            {
                throw new ArgumentException("Temperature cannot be less than absolute zero.");
            }
            else
            {
                m_value = value;
            }
        }
    }

    public Temperature(double kelvins)
    {
        this.Kelvin = kelvins;
    }
}

public class Example
{
    public static void Main()
    {
        SortedList<Temperature, string> temps = 
            new SortedList<Temperature, string>();

        // Add entries to the sorted list, out of order.
        temps.Add(new Temperature(2017.15), "Boiling point of Lead");
        temps.Add(new Temperature(0), "Absolute zero");
        temps.Add(new Temperature(273.15), "Freezing point of water");
        temps.Add(new Temperature(5100.15), "Boiling point of Carbon");
        temps.Add(new Temperature(373.15), "Boiling point of water");
        temps.Add(new Temperature(600.65), "Melting point of Lead");

        foreach( KeyValuePair<Temperature, string> kvp in temps )
        {
            Console.WriteLine("{0} is {1} degrees Celsius.", kvp.Value, kvp.Key.Celsius);
        }
    }
}
/* This example displays the following output:
      Absolute zero is -273.15 degrees Celsius.
      Freezing point of water is 0 degrees Celsius.
      Boiling point of water is 100 degrees Celsius.
      Melting point of Lead is 327.5 degrees Celsius.
      Boiling point of Lead is 1744 degrees Celsius.
      Boiling point of Carbon is 4827 degrees Celsius.
*/
Imports System.Collections.Generic

Public Class Temperature
    Implements IComparable(Of Temperature)

    ' Implement the generic CompareTo method with the Temperature class 
    ' as the type parameter. 
    '
    Public Overloads Function CompareTo(ByVal other As Temperature) As Integer _
        Implements IComparable(Of Temperature).CompareTo

        ' If other is not a valid object reference, this instance is greater.
        If other Is Nothing Then Return 1
        
        ' The temperature comparison depends on the comparison of the
        ' the underlying Double values. 
        Return m_value.CompareTo(other.m_value)
    End Function
    
    ' Define the is greater than operator.
    Public Shared Operator >  (operand1 As Temperature, operand2 As Temperature) As Boolean
       Return operand1.CompareTo(operand2) = 1
    End Operator
    
    ' Define the is less than operator.
    Public Shared Operator <  (operand1 As Temperature, operand2 As Temperature) As Boolean
       Return operand1.CompareTo(operand2) = -1
    End Operator

    ' Define the is greater than or equal to operator.
    Public Shared Operator >=  (operand1 As Temperature, operand2 As Temperature) As Boolean
       Return operand1.CompareTo(operand2) >= 0
    End Operator
    
    ' Define the is less than operator.
    Public Shared Operator <=  (operand1 As Temperature, operand2 As Temperature) As Boolean
       Return operand1.CompareTo(operand2) <= 0
    End Operator

    ' The underlying temperature value.
    Protected m_value As Double = 0.0

    Public ReadOnly Property Celsius() As Double
        Get
            Return m_value - 273.15
        End Get
    End Property

    Public Property Kelvin() As Double
        Get
            Return m_value
        End Get
        Set(ByVal Value As Double)
            If value < 0.0 Then 
                Throw New ArgumentException("Temperature cannot be less than absolute zero.")
            Else
                m_value = Value
            End If
        End Set
    End Property

    Public Sub New(ByVal kelvins As Double)
        Me.Kelvin = kelvins 
    End Sub
End Class

Public Class Example
    Public Shared Sub Main()
        Dim temps As New SortedList(Of Temperature, String)

        ' Add entries to the sorted list, out of order.
        temps.Add(New Temperature(2017.15), "Boiling point of Lead")
        temps.Add(New Temperature(0), "Absolute zero")
        temps.Add(New Temperature(273.15), "Freezing point of water")
        temps.Add(New Temperature(5100.15), "Boiling point of Carbon")
        temps.Add(New Temperature(373.15), "Boiling point of water")
        temps.Add(New Temperature(600.65), "Melting point of Lead")

        For Each kvp As KeyValuePair(Of Temperature, String) In temps
            Console.WriteLine("{0} is {1} degrees Celsius.", kvp.Value, kvp.Key.Celsius)
        Next
    End Sub
End Class

' The example displays the following output:
'      Absolute zero is -273.15 degrees Celsius.
'      Freezing point of water is 0 degrees Celsius.
'      Boiling point of water is 100 degrees Celsius.
'      Melting point of Lead is 327.5 degrees Celsius.
'      Boiling point of Lead is 1744 degrees Celsius.
'      Boiling point of Carbon is 4827 degrees Celsius.
'

備註

此介面由可以排列或排序其值的型別所實作,並提供強型別的比較方法,來排序的泛型集合物件的成員。This interface is implemented by types whose values can be ordered or sorted and provides a strongly typed comparison method for ordering members of a generic collection object. 例如,一個數字可能會大於第二個數字,和一個字串可以出現在另一個之前的字母順序。For example, one number can be larger than a second number, and one string can appear in alphabetical order before another. 它需要實作的類型會定義單一方法CompareTo(T),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(T), 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. 一般而言,直接從開發人員程式碼不被呼叫方法。Typically, the method is not called directly from developer code. 相反地,它會自動呼叫方法這類List<T>.Sort()AddInstead, it is called automatically by methods such as List<T>.Sort() and Add.

一般而言,型別,提供IComparable<T>實作也實作IEquatable<T>介面。Typically, types that provide an IComparable<T> implementation also implement the IEquatable<T> interface. IEquatable<T>介面會定義Equals方法,可判斷是否相等的實作類型的執行個體。The IEquatable<T> interface defines the Equals method, which determines the equality of instances of the implementing type.

實作CompareTo(T)方法必須傳回Int32具有三個值之一下, 表所示。The implementation of the CompareTo(T) 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 此物件位於所指定的物件CompareTo在排序次序的方法。This object 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方法引數。This current instance occurs in the same position in the sort order as the object specified by the CompareTo method argument.
大於零Greater than zero 此目前執行個體所指定的物件會遵循CompareTo方法引數,在排序次序。This current instance follows the object specified by the CompareTo method argument in the sort order.

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

給實施者的注意事項

取代的型別參數IComparable<T>介面實作這個介面的型別。Replace the type parameter of the IComparable<T> interface with the type that is implementing this interface.

如果您實作IComparable<T>,您應該多載op_GreaterThanop_GreaterThanOrEqualop_LessThan,並op_LessThanOrEqual運算子傳回值,都必須配合CompareTo(T)If you implement IComparable<T>, you should overload the op_GreaterThan, op_GreaterThanOrEqual, op_LessThan, and op_LessThanOrEqual operators to return values that are consistent with CompareTo(T). 此外,您也應該實作IEquatable<T>In addition, you should also implement IEquatable<T>. 請參閱IEquatable<T>文章的完整資訊。See the IEquatable<T> article for complete information.

方法

CompareTo(T) CompareTo(T) CompareTo(T) CompareTo(T)

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

另請參閱