IEnumerator.Reset IEnumerator.Reset IEnumerator.Reset IEnumerator.Reset Method

定义

将枚举数设置为其初始位置,该位置位于集合中第一个元素之前。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 ()

异常

集合在枚举器创建后被修改。The collection was modified after the enumerator was created.

示例

下面的代码示例演示如何实现IEnumerator自定义集合的接口。The following code example demonstrates the implementation of the IEnumerator interfaces for a custom collection. 在此示例中Reset , 未显式调用, 但实现它是为了支持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). 此代码示例摘自一个更大的IEnumerator接口示例。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

注解

如果对集合进行了更改 (如添加、修改或删除元素), Reset则的行为是不确定的。If changes are made to the collection, such as adding, modifying, or deleting elements, the behavior of Reset is undefined.

提供Reset此方法是为了实现 COM 互操作性。The Reset method is provided for COM interoperability. 它不一定需要实现;相反, 实施者可以直接引发NotSupportedExceptionIt does not necessarily need to be implemented; instead, the implementer can simply throw a NotSupportedException.

实施者说明

Reset()的所有调用都必须为枚举器生成相同的状态。All calls to Reset() must result in the same state for the enumerator. 首选的实现是在第一个元素之前将枚举器移动到集合的开头。The preferred implementation is to move the enumerator to the beginning of the collection, before the first element. 如果在创建枚举器后对集合进行了修改, 则此操作将使枚举器失效MoveNext() , Current这与和一致。This invalidates the enumerator if the collection has been modified since the enumerator was created, which is consistent with MoveNext() and Current.

适用于

另请参阅