IEnumerator.Reset メソッド


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.

 void Reset();
public void Reset ();
abstract member Reset : unit -> unit
Public Sub Reset ()


コレクションは、列挙子の作成後に変更されました。The collection was modified after the enumerator was created.

次のコード例は、カスタムコレクションのインターフェイスの実装を示して IEnumerator います。The following code example demonstrates the implementation of the IEnumerator interfaces for a custom collection. この例で Reset は、は明示的に呼び出されませんが、(Visual Basic) の使用をサポートするように実装されてい foreach for each ます。In this example, Reset is not explicitly called, but it is implemented to support the use of foreach (for each in Visual Basic). このコード例は、インターフェイスのより大きな例の一部です IEnumeratorThis code example is part of a larger example for the IEnumerator interface.

// 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();
' 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


要素の追加、変更、削除などの変更がコレクションに対して行われた場合、の動作 Reset は未定義になります。If changes are made to the collection, such as adding, modifying, or deleting elements, the behavior of Reset is undefined.

メソッドは、 Reset COM 相互運用性のために用意されています。The Reset method is provided for COM interoperability. 必ずしも実装する必要はありません。代わりに、実装者はをスローするだけで済み NotSupportedException ます。It does not necessarily need to be implemented; instead, the implementer can simply throw a NotSupportedException.

注意 (実装者)

Reset() を呼び出した結果は、列挙子にとって常に同じ状態になる必要があります。All calls to Reset() must result in the same state for the enumerator. 列挙子をコレクションの先頭、つまり先頭の要素の前に移動するような実装を推奨します。The preferred implementation is to move the enumerator to the beginning of the collection, before the first element. そうすると、列挙子の作成後にコレクションが変更されていた場合は列挙子が無効になり、MoveNext() および Current との一貫性が保たれます。This invalidates the enumerator if the collection has been modified since the enumerator was created, which is consistent with MoveNext() and Current.