IEnumerable Interfaccia

Definizione

Espone un enumeratore, che supporta un'iterazione semplice su una raccolta non generica.Exposes an enumerator, which supports a simple iteration over a non-generic collection.

public interface class IEnumerable
[System.Runtime.InteropServices.ComVisible(true)]
[System.Runtime.InteropServices.Guid("496B0ABE-CDEE-11d3-88E8-00902754C43A")]
public interface IEnumerable
type IEnumerable = interface
Public Interface IEnumerable
Derivato
Attributi

Esempi

Nell'esempio di codice seguente viene illustrata la procedura consigliata per l'iterazione IEnumerable di IEnumerator una raccolta personalizzata mediante l'implementazione delle interfacce e.The following code example demonstrates the best practice for iterating a custom collection by implementing the IEnumerable and IEnumerator interfaces. In questo esempio, i membri di queste interfacce non vengono chiamati in modo esplicito, ma sono implementati per supportare foreach l'For Each uso di (in Visual Basic) per scorrere la raccolta.In this example, members of these interfaces are not explicitly called, but they are implemented to support the use of foreach (For Each in Visual Basic) to iterate through the collection. Questo esempio è un'app console completa.This example is a complete Console app. Per compilare l'app Visual Basic, impostare l' oggetto di avvio su Sub Main nella pagina proprietà del progetto.To compile the Visual Basic app, change the Startup object to Sub Main in the project's Properties page.

Per un esempio che illustra come implementare l' IEnumerable interfaccia, vedere implementazione dell'interfaccia IEnumerable in una classe CollectionFor a sample that shows how to implement the IEnumerable interface, see Implementing the IEnumerable Interface in a Collection Class

using System;
using System.Collections;

// Simple business object.
public class Person
{
    public Person(string fName, string lName)
    {
        this.firstName = fName;
        this.lastName = lName;
    }

    public string firstName;
    public string lastName;
}

// Collection of Person objects. This class
// implements IEnumerable so that it can be used
// with ForEach syntax.
public class People : IEnumerable
{
    private Person[] _people;
    public People(Person[] pArray)
    {
        _people = new Person[pArray.Length];

        for (int i = 0; i < pArray.Length; i++)
        {
            _people[i] = pArray[i];
        }
    }

// Implementation for the GetEnumerator method.
    IEnumerator IEnumerable.GetEnumerator()
    {
       return (IEnumerator) GetEnumerator();
    }

    public PeopleEnum GetEnumerator()
    {
        return new PeopleEnum(_people);
    }
}

// When you implement IEnumerable, you must also implement IEnumerator.
public class PeopleEnum : IEnumerator
{
    public Person[] _people;

    // Enumerators are positioned before the first element
    // until the first MoveNext() call.
    int position = -1;

    public PeopleEnum(Person[] list)
    {
        _people = list;
    }

    public bool MoveNext()
    {
        position++;
        return (position < _people.Length);
    }

    public void Reset()
    {
        position = -1;
    }

    object IEnumerator.Current
    {
        get
        {
            return Current;
        }
    }

    public Person Current
    {
        get
        {
            try
            {
                return _people[position];
            }
            catch (IndexOutOfRangeException)
            {
                throw new InvalidOperationException();
            }
        }
    }
}

class App
{
    static void Main()
    {
        Person[] peopleArray = new Person[3]
        {
            new Person("John", "Smith"),
            new Person("Jim", "Johnson"),
            new Person("Sue", "Rabon"),
        };

        People peopleList = new People(peopleArray);
        foreach (Person p in peopleList)
            Console.WriteLine(p.firstName + " " + p.lastName);

    }
}

/* This code produces output similar to the following:
 *
 * John Smith
 * Jim Johnson
 * Sue Rabon
 *
 */
Imports System.Collections

' Simple business object.
Public Class Person

    Public Sub New(ByVal fName As String, ByVal lName As String)
        Me.firstName = fName
        Me.lastName = lName
    End Sub


    Public firstName As String
    Public lastName As String
End Class

' Collection of Person objects, which implements IEnumerable so that
' it can be used with ForEach syntax.
Public Class People
    Implements IEnumerable

    Private _people() As Person

    Public Sub New(ByVal pArray() As Person)
        _people = New Person(pArray.Length - 1) {}

        Dim i As Integer
        For i = 0 To pArray.Length - 1
            _people(i) = pArray(i)
        Next i
    End Sub

    ' Implementation of GetEnumerator.
    Public Function GetEnumerator() As IEnumerator _
      Implements IEnumerable.GetEnumerator

        Return New PeopleEnum(_people)
    End Function

End Class

' When you implement IEnumerable, you must also implement IEnumerator.
Public Class PeopleEnum
    Implements IEnumerator

    Public _people() As Person

    ' Enumerators are positioned before the first element
    ' until the first MoveNext() call.
    Dim position As Integer = -1

    Public Sub New(ByVal list() As Person)
        _people = list
    End Sub

    Public Function MoveNext() As Boolean Implements IEnumerator.MoveNext
        position = position + 1
        Return (position < _people.Length)
    End Function

    Public Sub Reset() Implements IEnumerator.Reset
        position = -1
    End Sub

    Public ReadOnly Property Current() As Object Implements IEnumerator.Current
        Get
            Try
                Return _people(position)
            Catch ex As IndexOutOfRangeException
                Throw New InvalidOperationException()
            End Try
        End Get
    End Property
End Class

Class App
    Shared Sub Main()
        Dim peopleArray() As Person = { _
            New Person("John", "Smith"), _
            New Person("Jim", "Johnson"), _
            New Person("Sue", "Rabon")}

        Dim peopleList As New People(peopleArray)
        Dim p As Person
        For Each p In peopleList
            Console.WriteLine(p.firstName + " " + p.lastName)
        Next

    End Sub
End Class

' This code produces output similar to the following:
' 
' John Smith
' Jim Johnson
' Sue Rabon

Commenti

IEnumerableè l'interfaccia di base per tutte le raccolte non generiche che possono essere enumerate.IEnumerable is the base interface for all non-generic collections that can be enumerated. Per la versione generica di questa interfaccia System.Collections.Generic.IEnumerable<T>, vedere.For the generic version of this interface see System.Collections.Generic.IEnumerable<T>. IEnumerablecontiene un solo metodo, GetEnumerator, che restituisce un IEnumeratoroggetto.IEnumerable contains a single method, GetEnumerator, which returns an IEnumerator. IEnumeratorfornisce la possibilità di scorrere la raccolta esponendo una Current proprietà e MoveNext i metodi Reset e.IEnumerator provides the ability to iterate through the collection by exposing a Current property and MoveNext and Reset methods.

È IEnumerable consigliabile implementare IEnumerable e IEnumerator sulle classi di raccolta per abilitare la sintassi (For Each in Visual Basic foreach ), tuttavia l'implementazione di non è obbligatoria.It is a best practice to implement IEnumerable and IEnumerator on your collection classes to enable the foreach (For Each in Visual Basic) syntax, however implementing IEnumerable is not required. Se la raccolta non implementa IEnumerable, è comunque necessario seguire il modello iteratore per supportare questa sintassi fornendo un GetEnumerator metodo che restituisce un'interfaccia, una classe o uno struct.If your collection does not implement IEnumerable, you must still follow the iterator pattern to support this syntax by providing a GetEnumerator method that returns an interface, class or struct. Quando si utilizza Visual Basic, è necessario fornire IEnumerator un'implementazione di, che viene GetEnumeratorrestituita da.When using Visual Basic, you must provide an IEnumerator implementation, which is returned by GetEnumerator. Quando si sviluppa C# con è necessario fornire una classe che contiene Current una proprietà e MoveNext i Reset metodi e come descritto IEnumeratorin, ma la classe non deve implementare IEnumerator.When developing with C# you must provide a class that contains a Current property, and MoveNext and Reset methods as described by IEnumerator, but the class does not have to implement IEnumerator.

Metodi

GetEnumerator()

Restituisce un enumeratore che consente di eseguire l'iterazione di una raccolta.Returns an enumerator that iterates through a collection.

Metodi di estensione

Cast<TResult>(IEnumerable)

Esegue il cast degli elementi di un oggetto IEnumerable nel tipo specificato.Casts the elements of an IEnumerable to the specified type.

OfType<TResult>(IEnumerable)

Filtra gli elementi di un oggetto IEnumerable in base a un tipo specificato.Filters the elements of an IEnumerable based on a specified type.

AsParallel(IEnumerable)

Consente la parallelizzazione di una query.Enables parallelization of a query.

AsQueryable(IEnumerable)

Converte un oggetto IEnumerable in un oggetto IQueryable.Converts an IEnumerable to an IQueryable.

Si applica a

Vedi anche