IEnumerable IEnumerable IEnumerable IEnumerable Interface

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

L'esempio di codice seguente illustra le procedure consigliate per l'iterazione di una raccolta personalizzata implementando il IEnumerable e IEnumerator interfacce.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 indicati esplicitamente, ma vengono implementate per supportare l'uso di foreach (For Each 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 le app Visual Basic, modificare il oggetto di avvio al Sub Main del progetto proprietà pagina.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 il IEnumerable dell'interfaccia, vedere che implementa l'interfaccia IEnumerable in una classe di raccoltaFor 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
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

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

È consigliabile implementare IEnumerable e IEnumerator in classi di raccolte per abilitare il foreach (For Each in Visual Basic) informazioni sulla sintassi, implementazione, tuttavia IEnumerable non è obbligatorio.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 di iteratore per supportare questa sintassi, fornendo un GetEnumerator metodo che restituisce un'interfaccia, una classe o 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 usa Visual Basic, è necessario fornire un' IEnumerator implementazione, che viene restituito dal GetEnumerator.When using Visual Basic, you must provide an IEnumerator implementation, which is returned by GetEnumerator. Quando lo sviluppo con c# è necessario fornire una classe che contiene un Current proprietà, e MoveNext e Reset metodi come descritto dalla IEnumerator, ma la classe non è necessario 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() GetEnumerator() GetEnumerator() GetEnumerator()

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

Extension Methods

Cast<TResult>(IEnumerable) Cast<TResult>(IEnumerable) Cast<TResult>(IEnumerable) 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) OfType<TResult>(IEnumerable) OfType<TResult>(IEnumerable) 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) AsParallel(IEnumerable) AsParallel(IEnumerable) AsParallel(IEnumerable)

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

AsQueryable(IEnumerable) AsQueryable(IEnumerable) AsQueryable(IEnumerable) AsQueryable(IEnumerable)

Converte un' IEnumerable a un IQueryable.Converts an IEnumerable to an IQueryable.

Si applica a

Vedi anche