IEnumerable IEnumerable IEnumerable IEnumerable Interface


公開能逐一查看非泛型集合內容一次的列舉程式。Exposes an enumerator, which supports a simple iteration over a non-generic collection.

public interface class IEnumerable
public interface IEnumerable
type IEnumerable = interface
Public Interface IEnumerable


下列程式碼範例示範如何逐一查看所實作的自訂集合的最佳做法IEnumerableIEnumerator介面。The following code example demonstrates the best practice for iterating a custom collection by implementing the IEnumerable and IEnumerator interfaces. 在此範例中,這些介面的成員不會明確呼叫,但它們會實作以支援使用foreach(For Each Visual Basic 中) 來逐一查看集合。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. 這個範例是完整的主控台應用程式。This example is a complete Console app. 若要編譯 Visual Basic 應用程式,變更啟始物件Sub Main在專案的屬性頁面。To compile the Visual Basic app, change the Startup object to Sub Main in the project's Properties page.

如需範例,示範如何實作IEnumerable介面,請參閱集合類別中實作 IEnumerable 介面For 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()
        return (position < _people.Length);

    public void Reset()
        position = -1;

    object IEnumerator.Current
            return Current;

    public Person Current
                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
                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)

    End Sub
End Class

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


IEnumerable 是可列舉的所有非泛型集合的基底介面。IEnumerable is the base interface for all non-generic collections that can be enumerated. 此介面的泛型版本,請參閱System.Collections.Generic.IEnumerable<T>For the generic version of this interface see System.Collections.Generic.IEnumerable<T>. IEnumerable 包含單一方法GetEnumerator,以傳回IEnumeratorIEnumerable contains a single method, GetEnumerator, which returns an IEnumerator. IEnumerator 讓您能夠藉由公開逐一查看集合Current屬性和MoveNextReset方法。IEnumerator provides the ability to iterate through the collection by exposing a Current property and MoveNext and Reset methods.

實作最佳的作法是IEnumerableIEnumerator在您的集合類別,以啟用foreach(For Each Visual Basic 中) 語法,但是實作IEnumerable不需要。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. 如果您的集合不會實作IEnumerable,您仍然必須遵循以支援此語法所提供的迭代器模式GetEnumerator傳回的介面、 類別或結構的方法。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. 當使用 Visual Basic,您必須提供IEnumerator實作,這由GetEnumeratorWhen using Visual Basic, you must provide an IEnumerator implementation, which is returned by GetEnumerator. 使用 C# 開發必須時提供類別,其中包含Current屬性,並MoveNextReset所述的方法IEnumerator,但類別沒有實作IEnumeratorWhen 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.


GetEnumerator() GetEnumerator() GetEnumerator() GetEnumerator()

傳回逐一查看集合的列舉值。Returns an enumerator that iterates through a collection.

Extension Methods

Cast<TResult>(IEnumerable) Cast<TResult>(IEnumerable) Cast<TResult>(IEnumerable) Cast<TResult>(IEnumerable)

IEnumerable 的項目轉換成指定的型別。Casts the elements of an IEnumerable to the specified type.

OfType<TResult>(IEnumerable) OfType<TResult>(IEnumerable) OfType<TResult>(IEnumerable) OfType<TResult>(IEnumerable)

篩選的項目IEnumerable根據指定的型別。Filters the elements of an IEnumerable based on a specified type.

AsParallel(IEnumerable) AsParallel(IEnumerable) AsParallel(IEnumerable) AsParallel(IEnumerable)

啟用查詢的平行化作業。Enables parallelization of a query.

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

將轉換IEnumerableIQueryableConverts an IEnumerable to an IQueryable.