How to manage the SAS information in .NET client library

I want to manage SAS info in .NET client library, including add a new rule to the topic, modify the exist rule, or even delete. Is this possible?

From my practice, I can only add a new rule before the very first time I create the topic.

NamespaceManager nm = NamespaceManager.CreateFromConnectionString(nsConnectionString);
contosoTListenRule = new SharedAccessAuthorizationRule("contosoTListenKey2",
    SharedAccessAuthorizationRule.GenerateRandomKey(),
    new[] { AccessRights.Listen });
TopicDescription td = new TopicDescription(topicPath);
td.Authorization.Add(contosoTListenRule);


nm.CreateTopic(td);