IComparable<T> 介面

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>
public interface IComparable<T>
type IComparable<'T> = interface
Public Interface IComparable(Of In T)
Public Interface IComparable(Of T)

類型參數

T

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

這是反變數的型別參數。 也就是說,您可以使用您指定的類型,或衍生程度較低的任何類型。 如需共變數與反變數的詳細資訊,請參閱泛型中的共變數與反變數
衍生

範例

下列範例說明簡單物件的執行 IComparable<T> TemperatureThe following example illustrates the implementation of IComparable<T> for a simple Temperature object. 此範例會 SortedList<TKey,TValue> 使用物件索引鍵來建立字串的集合 Temperature ,並將陣列溫度和字串新增至清單中的順序。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 SortedList<TKey,TValue> 時,集合 IComparable<T> 會使用實作為清單專案的排序,然後依提高溫度的順序顯示這些專案。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

這個介面是由可以排序或排序值的型別所執行,並提供強型別比較方法來排序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,一個數位可以大於第二個數字,一個字串可以依字母順序出現在另一個字串之前。For example, one number can be larger than a second number, and one string can appear in alphabetical order before another. 它要求實作為型別定義單一方法, CompareTo(T) 指出目前實例在排序次序中的位置是在相同類型的第二個物件之前、之後還是相同的。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,不會直接從開發人員程式碼呼叫方法。Typically, the method is not called directly from developer code. 相反地,它是由和這類方法自動呼叫 List<T>.Sort() AddInstead, it is called automatically by methods such as List<T>.Sort() and Add.

通常,提供實作為的型別 IComparable<T> 也會執行 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,此方法會決定實類型實例的相等性。The IEquatable<T> interface defines the Equals method, which determines the equality of instances of the implementing type.

方法的執行 CompareTo(T) 必須傳回 Int32 具有下列三個值之一的,如下表所示。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 這個物件會在排序次序的方法所指定的物件之前 CompareToThis object precedes the object specified by the CompareTo method in the sort order.
Zero 這個目前的實例會出現在排序次序中與方法引數所指定的物件相同的位置 CompareToThis 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 這個目前 CompareTo 的實例在排序次序中的方法引數所指定的物件之後。This current instance follows the object specified by the CompareTo method argument in the sort order.

所有數數值型別 (例如 Int32 和) 會實 Double IComparable<T> 作為 StringCharDateTimeAll numeric types (such as Int32 and Double) implement IComparable<T>, as do String, Char, and DateTime. 自訂類型也應該提供自己的實 IComparable<T> 作為,讓物件實例得以排序或排序。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

將介面的類型參數取代 IComparable<T> 為正在執行這個介面的型別。Replace the type parameter of the IComparable<T> interface with the type that is implementing this interface.

如果您要執行 IComparable<T> ,您應該多載 op_GreaterThan 、、 op_GreaterThanOrEqual op_LessThanop_LessThanOrEqual 運算子,以傳回與一致的值 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,您也應該實行 IEquatable<T>In addition, you should also implement IEquatable<T>. 如需 IEquatable<T> 完整資訊,請參閱文章。See the IEquatable<T> article for complete information.

方法

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