Sets the enumerator to its initial position, which is before the first element in the System.Security.Cryptography.X509Certificates.X509ExtensionCollection.
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 X509ExtensionEnumerator.MoveNext or X509ExtensionEnumerator.Reset throws an InvalidOperationException.