IEnumerator IEnumerator IEnumerator IEnumerator Interface

定義

非ジェネリック コレクションに対する単純な反復処理をサポートします。Supports a simple iteration over a non-generic collection.

public interface class IEnumerator
[System.Runtime.InteropServices.ComVisible(true)]
[System.Runtime.InteropServices.Guid("496B0ABF-CDEE-11d3-88E8-00902754C43A")]
public interface IEnumerator
type IEnumerator = interface
Public Interface IEnumerator
派生
属性

次のコード例の実装を示します、IEnumerableIEnumeratorカスタム コレクション用のインターフェイス。The following code example demonstrates the implementation of the IEnumerable and IEnumerator interfaces for a custom collection. この例では、これらのインターフェイスのメンバーは明示的に呼び出されないの使用をサポートするために実装されるforeach(for each Visual Basic で) コレクションを反復処理します。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.

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
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

注釈

IEnumerator すべての非ジェネリック列挙子は、基本インターフェイスです。IEnumerator is the base interface for all non-generic enumerators. 同等のジェネリックは、System.Collections.Generic.IEnumerator<T>インターフェイス。Its generic equivalent is the System.Collections.Generic.IEnumerator<T> interface.

C# 言語の foreach ステートメント (Visual Basic の場合は for each) を使用することで列挙子の複雑さを回避できます。The foreach statement of the C# language (for each in Visual Basic) hides the complexity of the enumerators. したがってを使用してforeach列挙子を直接操作するのではなくをお勧めします。Therefore, using foreach is recommended instead of directly manipulating the enumerator.

列挙子を使用すると、コレクション内のデータを読み取ることができますが、基になるコレクションを変更することはできません。Enumerators can be used to read the data in the collection, but they cannot be used to modify the underlying collection.

Reset実装側が代わりに、スローできます。 メソッドが COM 相互運用性は提供されており、完全に実装する必要はありません、NotSupportedExceptionします。The Reset method is provided for COM interoperability and does not need to be fully implemented; instead, the implementer can throw a NotSupportedException.

最初に、列挙子はコレクション内の 1 番目の要素の前に位置付けられます。Initially, the enumerator is positioned before the first element in the collection. 呼び出す必要があります、MoveNextメソッドの値を読み取る前に、コレクションの最初の要素を列挙子を進めるCurrent、それ以外のCurrentが定義されていません。You must call the MoveNext method to advance the enumerator to the first element of the collection before reading the value of Current; otherwise, Current is undefined.

Current は、MoveNext または Reset が呼び出されるまでは同じオブジェクトを返します。Current returns the same object until either MoveNext or Reset is called. MoveNext は、Current を次の要素に設定します。MoveNext sets Current to the next element.

場合MoveNext列挙子、コレクションの末尾がコレクション内の最後の要素の後に配置されているパスとMoveNext返しますfalseします。If MoveNext passes the end of the collection, the enumerator is positioned after the last element in the collection and MoveNext returns false. この位置では、後続の呼び出しで列挙子の場合MoveNextを返すこともfalseします。When the enumerator is at this position, subsequent calls to MoveNext also return false. 最後の呼び出し場合MoveNext返されるfalseCurrentが定義されていません。If the last call to MoveNext returned false, Current is undefined.

設定するCurrent再度、コレクションの最初の要素を呼び出すことができますResetを実装する場合は、続くMoveNextします。To set Current to the first element of the collection again, you can call Reset, if it's implemented, followed by MoveNext. 場合Resetが実装されていないコレクションの最初の要素を返す新しい列挙子インスタンスを作成する必要があります。If Reset is not implemented, you must create a new enumerator instance to return to the first element of the collection.

追加、変更、または、要素を削除するなど、コレクションに変更された場合、列挙子の動作は未定義です。If changes are made to the collection, such as adding, modifying, or deleting elements, the behavior of the enumerator is undefined.

列挙子にはコレクションへの排他アクセス権限はないため、コレクションの列挙処理は本質的にスレッド セーフな処理ではありません。The enumerator does not have exclusive access to the collection; therefore, enumerating through a collection is intrinsically not a thread-safe procedure. コレクションの同期がとられている場合でも、別のスレッドによってそのコレクションを変更できるため、変更の結果として列挙子は例外をスローします。Even when a collection is synchronized, other threads can still modify the collection, which causes the enumerator to throw an exception. 列挙処理を確実にスレッド セーフに行うには、列挙中にコレクションをロックするか、他のスレッドによって行われた変更によってスローされる例外をキャッチします。To guarantee thread safety during enumeration, you can either lock the collection during the entire enumeration or catch the exceptions resulting from changes made by other threads.

プロパティ

Current Current Current Current

列挙子の現在位置にあるコレクション内の要素を取得します。Gets the element in the collection at the current position of the enumerator.

メソッド

MoveNext() MoveNext() MoveNext() MoveNext()

列挙子をコレクションの次の要素に進めます。Advances the enumerator to the next element of the collection.

Reset() Reset() Reset() Reset()

列挙子を初期位置、つまりコレクションの最初の要素の前に設定します。Sets the enumerator to its initial position, which is before the first element in the collection.

適用対象

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