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


下列程式碼範例將示範如何藉由執行 IEnumerableIEnumerator 介面,逐一查看自訂集合的最佳做法。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,不會明確呼叫這些介面的成員,但會將它們實作為支援使用 foreach (在 Visual Basic 中For Each)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,請在專案的 [屬性] 頁面中,將 [啟始] 物件變更為 [ Sub Main ]。To compile the Visual Basic app, change the Startup object to Sub Main in the project's Properties page.

如需示範如何執行 IEnumerable 介面的範例,請參閱在集合類別中執行 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.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 是可列舉之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. 如需此介面的泛型版本,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,它會傳回 IEnumeratorIEnumerable contains a single method, GetEnumerator, which returns an IEnumerator. IEnumerator 提供藉由公開 Current 屬性和 MoveNextReset 方法,逐一查看集合的功能。IEnumerator provides the ability to iterate through the collection by exposing a Current property and MoveNext and Reset methods.

最佳做法是在您的集合類別上執行 IEnumerableIEnumerator,以啟用 foreachFor Each 在 Visual Basic)語法中,但不需要執行 IEnumerableIt 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. 如果您的集合未執行 IEnumerable,您仍然必須遵循反覆運算器模式來支援此語法,方法是提供傳回介面、類別或結構的 GetEnumerator 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. 使用 Visual Basic 時,您必須提供 GetEnumerator傳回的 IEnumerator 實作為。When using Visual Basic, you must provide an IEnumerator implementation, which is returned by GetEnumerator. 使用進行C#開發時,您必須提供包含 Current 屬性的類別,以及 IEnumerator所描述的 MoveNextReset 方法,但類別不需要執行 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.



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

Extension Methods


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


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


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


IEnumerable 轉換成 IQueryableConverts an IEnumerable to an IQueryable.

Applies to

See also