IEnumerator.MoveNext IEnumerator.MoveNext IEnumerator.MoveNext IEnumerator.MoveNext Method

定义

将枚举数推进到集合的下一个元素。Advances the enumerator to the next element of the collection.

public:
 bool MoveNext();
public bool MoveNext ();
abstract member MoveNext : unit -> bool
Public Function MoveNext () As Boolean

返回

如果枚举数已成功地推进到下一个元素,则为 true;如果枚举数传递到集合的末尾,则为 falsetrue if the enumerator was successfully advanced to the next element; false if the enumerator has passed the end of the collection.

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为自定义集合的接口。The following code example demonstrates the implementation of the IEnumerator interfaces for a custom collection. 在此示例中,MoveNext未显式调用,但它实现以支持使用foreach(for each在 Visual Basic 中)。In this example, MoveNext 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示例的IEnumerator接口。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

创建一个枚举器或Reset方法调用时,枚举器位于集合中,并在首次调用的第一个元素的前面MoveNext方法移到第一个元素的集合的枚举器。After an enumerator is created or after the Reset method is called, an enumerator is positioned before the first element of the collection, and the first call to the MoveNext method moves the enumerator over the first element of the collection.

如果MoveNext越过集合,枚举器的末尾放置在集合中的最后一个元素的后面和MoveNext返回falseIf MoveNext passes the end of the collection, the enumerator is positioned after the last element in the collection and MoveNext returns false. 当枚举数位于此位置上,对后续调用MoveNext也会返回false直到Reset调用。When the enumerator is at this position, subsequent calls to MoveNext also return false until Reset is called.

如果对集合中,如添加、 修改或删除元素的行为更改MoveNext是不确定的。If changes are made to the collection, such as adding, modifying, or deleting elements, the behavior of MoveNext is undefined.

适用于

另请参阅