in rocketmq-client-csharp/SimpleConsumer.cs [138:149]
public void Subscribe(string topic, rmq::FilterType filterType, string expression)
{
var entry = new rmq::SubscriptionEntry();
entry.Topic = new rmq::Resource();
entry.Topic.Name = topic;
entry.Topic.ResourceNamespace = ResourceNamespace;
entry.Expression = new rmq::FilterExpression();
entry.Expression.Type = filterType;
entry.Expression.Expression = expression;
_subscriptions.AddOrUpdate(topic, entry, (k, prev) => entry);
AddTopicOfInterest(topic);
}