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.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)
Syntax
<[%$TOPIC/h1x9x1b1_en-us_VS_110_1_0_0_0_0%](True)> _
<[%$TOPIC/h1x9x1b1_en-us_VS_110_1_0_0_0_1%]("496B0ABE-CDEE-11d3-88E8-00902754C43A")> _
Public Interface IEnumerable
[[%$TOPIC/h1x9x1b1_en-us_VS_110_1_0_1_0_0%](true)]
[[%$TOPIC/h1x9x1b1_en-us_VS_110_1_0_1_0_1%]("496B0ABE-CDEE-11d3-88E8-00902754C43A")]
public interface IEnumerable
[[%$TOPIC/h1x9x1b1_en-us_VS_110_1_0_2_0_0%](true)]
[[%$TOPIC/h1x9x1b1_en-us_VS_110_1_0_2_0_1%](L"496B0ABE-CDEE-11d3-88E8-00902754C43A")]
public interface class IEnumerable
[<[%$TOPIC/h1x9x1b1_en-us_VS_110_1_0_3_0_0%](true)>]
[<[%$TOPIC/h1x9x1b1_en-us_VS_110_1_0_3_0_1%]("496B0ABE-CDEE-11d3-88E8-00902754C43A")>]
type IEnumerable =  interface end

The IEnumerable type exposes the following members.

Methods
  NameDescription
Public method Supported by the XNA Framework Supported by Portable Class Library Supported in .NET for Windows Store apps GetEnumeratorReturns an enumerator that iterates through a collection.
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Extension Methods
  NameDescription
Public Extension Method Supported by Portable Class Library Supported in .NET for Windows Store apps AsParallelEnables parallelization of a query. (Defined by ParallelEnumerable.)
Public Extension Method Supported by Portable Class Library Supported in .NET for Windows Store apps AsQueryableConverts an IEnumerable to an IQueryable. (Defined by Queryable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Supported in .NET for Windows Store apps CastTResultCasts the elements of an IEnumerable to the specified type. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Supported in .NET for Windows Store apps OfTypeTResultFilters the elements of an IEnumerable based on a specified type. (Defined by Enumerable.)
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Remarks

For the generic version of this interface see System.Collections.GenericIEnumerableT.

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.

Examples

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.

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
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 (IEnumerator) GetEnumerator();
    }

    public PeopleEnum 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;
    }

    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
 *
 */
Version Information

.NET Framework

Supported in: 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8
Platforms

Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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