# IComparableIComparableIComparableIComparable Interface

## Definizione

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

## Esempi

Nell'esempio seguente viene illustrata l'implementazione IComparable di e il CompareTo metodo richiesto.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;
}

// 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;
}

// 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
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
``````

## Commenti

Questa interfaccia viene implementata dai tipi i cui valori possono essere ordinati o ordinati.This interface is implemented by types whose values can be ordered or sorted. Richiede che i tipi di implementazione definiscano un CompareTo(Object)singolo metodo,, che indica se la posizione dell'istanza corrente nell'ordinamento è precedente, successiva o uguale a un secondo oggetto dello stesso tipo.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. L' IComparable implementazione dell'istanza viene chiamata automaticamente da metodi Array.Sort quali e ArrayList.Sort.The instance's IComparable implementation is called automatically by methods such as Array.Sort and ArrayList.Sort.

L'implementazione del CompareTo(Object) metodo deve restituire un oggetto Int32 con uno dei tre valori, come illustrato nella tabella seguente.The implementation of the CompareTo(Object) method must return an Int32 that has one of three values, as shown in the following table.

ValueValue SignificatoMeaning
Minore di zeroLess than zero L'istanza corrente precede l'oggetto specificato dal CompareTo metodo nell'ordinamento.The current instance precedes the object specified by the CompareTo method in the sort order.
ZeroZero Questa istanza corrente si trova nella stessa posizione dell'oggetto specificato dal CompareTo metodo all'interno dell'ordinamento.This current instance occurs in the same position in the sort order as the object specified by the CompareTo method.
Maggiore di zeroGreater than zero Questa istanza corrente segue l'oggetto specificato dal CompareTo metodo nell'ordinamento.This current instance follows the object specified by the CompareTo method in the sort order.

Tutti i tipi numerici ( Int32 ad Doubleesempio e IComparable String) implementano, Charcome, DateTimee.All numeric types (such as Int32 and Double) implement IComparable, as do String, Char, and DateTime. I tipi personalizzati devono inoltre fornire la propria implementazione IComparable di per consentire l'ordinamento o l'ordinamento delle istanze degli oggetti.Custom types should also provide their own implementation of IComparable to enable object instances to be ordered or sorted.

## Metodi

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