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, 但实现它是为了支持foreach使用 (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

在创建枚举器之后或在调用Reset方法之后, 枚举数将定位在集合的第一个元素之前, 对MoveNext方法的第一次调用将枚举器移动到集合的第一个元素上。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越过集合的末尾, 则枚举器将定位在集合中最后一个元素之后, 并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. 当枚举器位于此位置时, 对MoveNext的后续调用也将返回false , 直到Reset调用。When the enumerator is at this position, subsequent calls to MoveNext also return false until Reset is called.

如果对集合进行了更改 (如添加、修改或删除元素), MoveNext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 MoveNext is undefined.

适用于

另请参阅