IEnumerator.Reset Method

public:
 void Reset();

public void Reset();

abstract member Reset : unit -> unit

Public Sub Reset ()

Exceptions

Examples

The following code example demonstrates the implementation of the IEnumerator interfaces for a custom collection. In this example, Reset 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

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

The Reset method is provided for COM interoperability. It does not necessarily need to be implemented; instead, the implementer can simply throw a NotSupportedException.

Notes to Implementers

All calls to Reset() must result in the same state for the enumerator. The preferred implementation is to move the enumerator to the beginning of the collection, before the first element. This invalidates the enumerator if the collection has been modified since the enumerator was created, which is consistent with MoveNext() and Current.

See also

• MoveNext()
• Current