Hi Zhen,
[quote user="Zhen Li"]your customer[/quote]
As other wrote already, I am not Bentley employee. And I am not sure based on what information you did such assumption ... and wrote wrong reaction.
[quote user="Zhen Li"]customer can not (does not allow) to access Ribbon bar.[/quote]
I did not write anything like this!
What I wrote is that for last several years (at least from first V8i release) Bentley have told clearly (I vaguely remember some BDN presentation and also discussion in communities) that dgnlib is the preferred way how to customize MicroStation both for users and developers. And despite of there are always some exceptions, the most of requirements for menu customization can be solved by dgnlib without big troubles.
It seems you did not search existing discussions, because Ribbon access was discussed several times in the past already. As I wrote (and also Maury, who I am sure has much better knowledge of CONNECT API than me), ribbon is just NET control, so you can access it if you don't want to use dgnlib. But you will have to find your own way and you will have to add NET code to you application.
[quote user="Zhen Li"]IS there any ways to allow your customers to call their MDL during editing their drawing?[/quote]
Yes, create own dgnlib, define button (or menu item) and call your key-in or mdl function from this button. Because dgnlib is the main MicroStation administration tools (everything is driven by dgnlib in V8i and CONNECT Edition: any styles, GUI, levels etc.) there are plenty of information available. You should start with information in CONNECT Edition help, in the case of V8i it's probably better to check Communities wiki, discussions and maybe also Bentley LEARN server.
To start to customize CONNECT Edition GUI is straightforward and simple, because without any configuration, the customization is stored into personal.dgnlib automatically. It's not good for development (personal is personal and not application dgnlib), but comparing to V8i there is no any block why not to just try it.
BTW In my opinion dgnlib knowledge is "must know" for MicroStation administrators and developers for last several years, so to invest time to learn it and to receive some experience is very good investment.
With regards,
Jan