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.NET Development
.NET Framework 3.5
This page is specific to
Microsoft Visual Studio 2008/.NET Framework 3.5

Other versions are also available for the following:
.NET Framework Class Library
IEnumerable Interface

Exposes the enumerator, which supports a simple iteration over a non-generic collection.

Namespace:  System.Collections
Assembly:  mscorlib (in mscorlib.dll)
Visual Basic (Declaration)
<ComVisibleAttribute(True)> _
<GuidAttribute("496B0ABE-CDEE-11d3-88E8-00902754C43A")> _
Public Interface IEnumerable
Visual Basic (Usage)
Dim instance As IEnumerable
C#
[ComVisibleAttribute(true)]
[GuidAttribute("496B0ABE-CDEE-11d3-88E8-00902754C43A")]
public interface IEnumerable
Visual C++
[ComVisibleAttribute(true)]
[GuidAttribute(L"496B0ABE-CDEE-11d3-88E8-00902754C43A")]
public interface class IEnumerable
JScript
public interface IEnumerable

For the generic version of this interface see System.Collections.Generic..::.IEnumerable<(Of <(T>)>).

Notes to Implementers:

IEnumerable must be implemented to support the foreach semantics of Microsoft Visual Basic. COM classes that allow enumerators also implement this interface.

The following code example demonstrates the implementation of the IEnumerable and IEnumerator interfaces for a custom collection. 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.

Visual Basic
Imports System
Imports System.Collections

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

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

    Public Function GetEnumerator() As IEnumerator _
      Implements IEnumerable.GetEnumerator

        Return New PeopleEnum(_people)
    End Function

End Class

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


C#
using System;
using System.Collections;

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

    public string firstName;
    public string lastName;
}

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];
        }
    }

        IEnumerator IEnumerable.GetEnumerator()
        {
            return new PeopleEnum(_people);
        }
}

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;
    }

    public object 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
 *
 */

Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0

XNA Framework

Supported in: 2.0, 1.0
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Refactored: generic list instead of object array, combined interfaces into one class, added indexer      jmlivingston ... ZSpecs   |   Edit   |  

using System;
using System.Collections;
using System.Collections.Generic;

namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
List<Person> peopleArray = new List<Person>()
{
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);

Person p2 = peopleList[1]; //Jim Johnson
Console.WriteLine(p2.firstName + " " + p2.lastName);
}
}

public class Person
{
public Person(string firstName, string lastName)
{
this.firstName = firstName;
this.lastName = lastName;
}

public string firstName;
public string lastName;
}

public class People : IEnumerable, IEnumerator
{
private List<Person> people;
int position = -1;
public People(List<Person> list)
{
people = list;
}

public Person this[int indexer]
{
get { return people[indexer]; }
set { people[indexer] = value; }
}

public bool MoveNext()
{
position++;
return (position < people.Count);
}

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

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

public IEnumerator GetEnumerator()
{
return new People(people);
}
}
}

OR you can just derive People from List&lt;Person&gt;      ZSpecs   |   Edit   |  
And it will work just fine.
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