IEnumerator.MoveNext Method

public:
 bool MoveNext();

public bool MoveNext();

abstract member MoveNext : unit -> bool

Public Function MoveNext () As Boolean

Returns

true if the enumerator was successfully advanced to the next element; false if the enumerator has passed the end of the collection.

Exceptions

Examples

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.

// 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

Remarks

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.

If changes are made to the collection, such as adding, modifying, or deleting elements, the behavior of MoveNext is undefined.

See also

• Current
• Reset()