IEnumerable Interface

Definição

Expõe um enumerador que dá suporte a uma iteração simples em uma coleção não genérica.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
Derivado
Atributos

Exemplos

O exemplo de código a seguir demonstra a prática recomendada para iterar uma coleção personalizada IEnumerable implementando as interfaces e IEnumerator .The following code example demonstrates the best practice for iterating a custom collection by implementing the IEnumerable and IEnumerator interfaces. Neste exemplo, os membros dessas interfaces não são chamados explicitamente, mas são implementados para dar suporte ao uso de foreach (For Each no Visual Basic) para iterar pela coleção.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. Este exemplo é um aplicativo de console completo.This example is a complete Console app. Para compilar o aplicativo Visual Basic, altere o objeto de inicialização para Sub Main na página de Propriedades do projeto.To compile the Visual Basic app, change the Startup object to Sub Main in the project's Properties page.

Para obter um exemplo que mostra como implementar a IEnumerable interface, consulte implementando a interface IEnumerable em uma classe de coleçãoFor 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

Comentários

IEnumerableé a interface base para todas as coleções não genéricas que podem ser enumeradas.IEnumerable is the base interface for all non-generic collections that can be enumerated. Para obter a versão genérica desta interface, System.Collections.Generic.IEnumerable<T>consulte.For the generic version of this interface see System.Collections.Generic.IEnumerable<T>. IEnumerablecontém um único método, GetEnumerator, que retorna um IEnumerator.IEnumerable contains a single method, GetEnumerator, which returns an IEnumerator. IEnumeratorfornece a capacidade de iterar pela coleção expondo uma Current propriedade Reset e MoveNext métodos.IEnumerator provides the ability to iterate through the collection by exposing a Current property and MoveNext and Reset methods.

É uma prática recomendada implementar IEnumerable e IEnumerator em suas classes de coleção para habilitar a foreach sintaxe (For Each em Visual Basic), no entanto IEnumerable , a implementação não é necessária.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 sua coleção não for implementada IEnumerable, você ainda deverá seguir o padrão de iterador para dar suporte a essa sintaxe, fornecendo um GetEnumerator método que retorna uma interface, classe ou estrutura.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. Ao usar Visual Basic, você deve fornecer uma IEnumerator implementação, que é retornada por GetEnumerator.When using Visual Basic, you must provide an IEnumerator implementation, which is returned by GetEnumerator. Ao desenvolver com C# , você deve fornecer uma classe que contenha uma Current propriedade MoveNext e Reset métodos e, conforme IEnumeratordescrito por, mas a classe não precisa implementar 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.

Métodos

GetEnumerator()

Retorna um enumerador que itera em uma coleção.Returns an enumerator that iterates through a collection.

Métodos de Extensão

Cast<TResult>(IEnumerable)

Converte os elementos de um IEnumerable para o tipo especificado.Casts the elements of an IEnumerable to the specified type.

OfType<TResult>(IEnumerable)

Filtra os elementos de um IEnumerable com base em um tipo especificado.Filters the elements of an IEnumerable based on a specified type.

AsParallel(IEnumerable)

Habilita a paralelização de uma consulta.Enables parallelization of a query.

AsQueryable(IEnumerable)

Converte um IEnumerable em um IQueryable.Converts an IEnumerable to an IQueryable.

Aplica-se a

Veja também