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

Definizione

Definisce un metodo di confronto generalizzato che viene implementato da un tipo di valore o da una classe per creare un metodo di confronto specifico del tipo per l'ordinamento delle istanze.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)

Parametri di tipo

T

Tipo di oggetto da confrontare.The type of object to compare.

Derivato

Esempi

Nell'esempio di codice riportato di seguito viene illustrata l'implementazione di IComparable<T> per un semplice oggetto Temperature.The following code example illustrates the implementation of IComparable<T> for a simple Temperature object. Nell'esempio viene creato un SortedList<TKey,TValue> insieme di stringhe con Temperature chiavi e aggiunge diverse coppie di temperature e stringhe fuori sequenza l'elenco.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. Nella chiamata alla Add , metodo di SortedList<TKey,TValue> viene utilizzata insieme la IComparable<T> implementazione per ordinare le voci di elenco, che vengono quindi visualizzate in ordine di temperatura crescente.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.
'

Commenti

Questa interfaccia viene implementata da tipi i cui valori possono essere ordinati e fornisce un metodo di confronto fortemente tipizzato per ordinare i membri di un oggetto insieme generico.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. Ad esempio, un numero può essere maggiore di un secondo numero e una stringa può essere visualizzata in ordine alfabetico prima di un'altra.For example, one number can be larger than a second number, and one string can appear in alphabetical order before another. Richiede che i tipi di implementazione definiscono un singolo metodo, CompareTo(T), che indica se la posizione dell'istanza corrente nella sequenza di ordinamento è precedente, dopo o uguale come un secondo oggetto dello stesso tipo.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. In genere, il metodo non viene chiamato direttamente dal codice dello sviluppatore.Typically, the method is not called directly from developer code. Invece chiamata automaticamente da metodi quali List<T>.Sort() e Add.Instead, it is called automatically by methods such as List<T>.Sort() and Add.

In genere, i tipi che forniscono un IComparable<T> implementazione anche l'implementazione di IEquatable<T> dell'interfaccia.Typically, types that provide an IComparable<T> implementation also implement the IEquatable<T> interface. Il IEquatable<T> l'interfaccia definisce il Equals metodo che determina l'uguaglianza fra istanze del tipo di implementazione.The IEquatable<T> interface defines the Equals method, which determines the equality of instances of the implementing type.

L'implementazione del CompareTo(T) metodo deve restituire un Int32 che presenta uno dei tre valori, come illustrato nella tabella seguente.The implementation of the CompareTo(T) method must return an Int32 that has one of three values, as shown in the following table.

ValueValue SignificatoMeaning
Minore di zeroLess than zero Questo oggetto precede l'oggetto specificato per il CompareTo metodo nell'ordinamento.This object precedes the object specified by the CompareTo method in the sort order.
ZeroZero L'istanza corrente è nella stessa posizione nell'ordinamento dell'oggetto specificato per il CompareTo argomento del metodo.This current instance occurs in the same position in the sort order as the object specified by the CompareTo method argument.
Maggiore di zeroGreater than zero L'istanza corrente segue l'oggetto specificato per il CompareTo argomento del metodo dell'ordinamento.This current instance follows the object specified by the CompareTo method argument in the sort order.

Tutti i tipi numerici (ad esempio Int32 e Double) implementare IComparable<T>, come le String, Char, e DateTime.All numeric types (such as Int32 and Double) implement IComparable<T>, as do String, Char, and DateTime. Tipi personalizzati devono anche fornire la propria implementazione di IComparable<T> per abilitare le istanze di oggetto deve essere ordinato o ordinato.Custom types should also provide their own implementation of IComparable<T> to enable object instances to be ordered or sorted.

Note per gli implementatori

Sostituire il parametro di tipo i IComparable<T> interfaccia con il tipo che implementa questa interfaccia.Replace the type parameter of the IComparable<T> interface with the type that is implementing this interface.

Se si implementa IComparable<T>, è necessario eseguire l'overload degli operatori op_GreaterThan, op_GreaterThanOrEqual, op_LessThan e op_LessThanOrEqual per restituire valori coerenti con 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). È inoltre necessario implementare IEquatable<T>.In addition, you should also implement IEquatable<T>. Per informazioni complete, vedere l'articolo IEquatable<T>.See the IEquatable<T> article for complete information.

Metodi

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

Confronta l'istanza corrente con un altro oggetto dello stesso tipo e restituisce un intero che indica se l'istanza corrente precede, segue o si trova nella stessa posizione dell'altro oggetto all'interno dell'ordinamento.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.

Si applica a

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