KeyinTree for MstnPlatformNet

Dear all, 

I am a newbie in MicrostationAPI (using C#). I am following Learning MicroStation Addins Step by Step to create an Addin. It seems MicroStationAPI has changed very much since the post was created. Therefore I got stuck in KeyinTree problem when trying to use commands.xml to structure commands.

In the post, they use parameter KeyinTree in namespace Bentley.Microstation. In the current MicroStationAPI, however, this namespace is replaced with Bentley.MstnPlatformNet (if I understand right, because I could not find Bentley.Microstation), therefore AddInAttribute definition no longer includes KeyinTree.

Could anyone tell me how I can handle this problem?

Thanks in advance.