IEnumerator.Reset 方法

定義

設定列舉值至它的初始位置,這是在集合中第一個項目之前。Sets the enumerator to its initial position, which is before the first element in the collection.

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

例外狀況

建立列舉值之後,集合已修改。The collection was modified after the enumerator was created.

範例

下列程式碼範例示範如何執行IEnumerator自訂集合的介面。The following code example demonstrates the implementation of the IEnumerator interfaces for a custom collection. 在此範例中Reset , 不會明確呼叫, 但會實作為支援foreach使用 (for each在 Visual Basic 中)。In this example, Reset is not explicitly called, but it is implemented to support the use of foreach (for each in Visual Basic). 這個程式碼範例是IEnumerator介面之較大範例的一部分。This 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()
    {
        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();
            }
        }
    }
}
' 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

備註

如果對集合進行了變更, 例如加入、修改或刪除元素, 則的行為Reset未定義。If changes are made to the collection, such as adding, modifying, or deleting elements, the behavior of Reset is undefined.

提供Reset COM 互通性的方法。The Reset method is provided for COM interoperability. 不一定需要實作為,相反地, 實施者只會擲NotSupportedException回。It does not necessarily need to be implemented; instead, the implementer can simply throw a NotSupportedException.

給實施者的注意事項

所有對Reset()的呼叫都必須為列舉值產生相同的狀態。All calls to Reset() must result in the same state for the enumerator. 慣用的實作為在第一個元素之前, 將列舉值移至集合的開頭。The preferred implementation is to move the enumerator to the beginning of the collection, before the first element. 如果已在建立枚舉器之後修改集合, 這與MoveNext()Current一致, 這會使列舉值失效。This invalidates the enumerator if the collection has been modified since the enumerator was created, which is consistent with MoveNext() and Current.

適用於

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