Assembly: mscorlib (in mscorlib.dll)
'Declaration Function MoveNext As Boolean 'Usage Dim instance As IEnumerator Dim returnValue As Boolean returnValue = instance.MoveNext
Return Valuetrue if the enumerator was successfully advanced to the next element; false if the enumerator has passed the end of the collection.
The collection was modified after the enumerator was created.
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.
If MoveNext passes the end of the collection, the enumerator is positioned after the last element in the collection and MoveNext returns false. When the enumerator is at this position, subsequent calls to MoveNext also return false until Reset is called.
An enumerator remains valid as long as the collection remains unchanged. If changes are made to the collection, such as adding, modifying, or deleting elements, the enumerator is irrecoverably invalidated and the next call to MoveNext or Reset throws an InvalidOperationException.
The following code example demonstrates the implementation of the IEnumerator interfaces for a custom collection. In this example, MoveNext is not explicitly called, but it is implemented to support the use of foreach (for each in Visual Basic). This code example is part of a larger example for the IEnumerator interface.
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
Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter EditionThe Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.