RavenDB Extension Method to generate an ID without storing the document

RavenExtensions.cs

public static string GenerateIdFor<T>(this IDocumentSession session)
{
  // We need the advanced session in order to ensure that the keys are generated in the correct database.
  // session.Advanced.DocumentStore.DatabaseCommands is not sufficient.
  var advancedSession = session.Advanced as DocumentSession;
  if (advancedSession == null)
    throw new InvalidOperationException();

  // An entity instance is required to generate a key, but we only have a type.
  // In our case, the entities don't have public constructors so we must use reflection.
  var entity = Activator.CreateInstance(typeof(T), true);

  // Generate an ID using the commands and conventions from the current session
  return advancedSession.Conventions.GenerateDocumentKey(advancedSession.DatabaseCommands, entity);
}

Usage: var id = session.GenerateIdFor();

Let's try that again (what, can't delete/edit a gist comment?)

Usage: var id = session.GenerateIdFor();