See Also: IEnumerator<T> Members
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Enumerators can be used to read the data in the collection, but they cannot be used to modify the underlying collection.
Initially, the enumerator is positioned before the first element in the collection. At this position, callingIEnumerator<T>.Current is unspecified. Therefore, you must call IEnumerator.MoveNext to advance the enumerator to the first element of the collection before reading the value of IEnumerator<T>.Current.
If IEnumerator.MoveNext passes the end of the collection, the enumerator is positioned after the last element in the collection and IEnumerator.MoveNext returns false. When the enumerator is at this position, subsequent calls to IEnumerator.MoveNext also return false. If the last call to IEnumerator.MoveNext returned false, calling IEnumerator<T>.Current is unspecified. You cannot set IEnumerator<T>.Current to the first element of the collection again; you must create a new enumerator instance instead.
An enumerator remains valid as long as the collection remains unchanged and the enumerator is not disposed. If changes are made to the collection, such as adding, modifying, or deleting elements, the enumerator is irrecoverably invalidated and its behavior is unspecified.
The enumerator does not have exclusive access to the collection; therefore, enumerating through a collection is intrinsically not a thread-safe procedure. To guarantee thread safety during enumeration, you can lock the collection during the entire enumeration. To allow the collection to be accessed by multiple threads for reading and writing, you must implement your own synchronization.
Default implementations of collections in System.Collections.Generic are not synchronized.
[Note: Implementing this interface requires implementing the non-generic interface IEnumerator. The methods MoveNext, Reset and Dispose do not depend on the type parameter T , and appear only on the non-generic interface IEnumerator. The property Current appears on both interfaces, but with different return types. Implementations should provide the non-generic Current property as an explicit interface member implementation. This allows any consumer of the non-generic interface to consume the generic interface.]