Sets the enumerator to its initial position, which is before the first element in the collection.
Assembly: System.AddIn.Contract (in System.AddIn.Contract.dll)
The collection was modified after the enumerator was created.
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 throws an InvalidOperationException.