Named Expression checks for Reference Slot Use

Hi Patrick,

I am not quite sure whether MicroStation Programming forum is not a better to place such question, because it's the question "in a middle" between customization (administration) and programming, but bigger part seems to be about development.

At the same time I'd like to express my good feeling from your post, because rarely the questions are so well structured and provide good overall picture. Just one information is missing: What MicroStation version do you use? It can be deduced from the screen capture it's probably V8i, but it's recommended to specify it exactly.

Unknown said:

I think the technique is to add a Show/Hide test on the tool definition.

In general yes, it's correct, but from reasons mentioned below I am not quite sure whether to use standard customization (custom toolbox + Named Expressions) is the best one.

Unknown said:

I haven't figured how to write the Named Expression it will require. I think this is simple, but I don't have the skills to do it myself.

Well, if you are skilled C# developer and you know how Named Expressions work internally, it's not very difficult. But in this specific case it's a bit more complex, because I suppose the reference slot number is not accessible from VBA, which is equal to COM API used by V8i NET code. It means C# code has to call MDL C functions to get this information (I guess MDL would be enough for it, but not sure).

Unknown said:

Where are some resources that can show me how to learn to make Named Expressions?

I recollect only one presentation from some BDN conference where it was explained how Named Expressions work internally and how own can be created. So the answer is "it's part of BDN resources", but I don't know whether these materials (presentations, examples, recordings...) are accessible as download even for BDN members.

Unknown said:

I really don't want the toolbar expanding and contracting in size to mess up my docked arrangements.

It sounds like a contradiction to your idea to use Show/Hide test, because when these tests will be applied, the toolbox will grow and shrink.

Unknown said:

Are these assumptions erroneous or good?

Mostly yes, but he problem is there is no such triggering in tool visbility test. If a tool should be displayed or not based on Named Expression test is evaluated when the toolbar is opened (once) and at every next opening, but not in any other case. But the events you mentioned can happen really often, especially number 3, because a reference can be displayed differently in different views, so e.g. a change of active view will produce a request to update the toolbar.

In conclusion:

It seems, using this way, you need:

• Own Named Expression symbol provider, which is NET assembly (dll file) and properly configured MicroStation (there is one variable responsible for NE).
• Dgnlib with the toolbar definition and with Named Expression definition.
• Separate application (native C or C++ code) that will monitor MicroStation events and will force show/hid visibility test reevalaution.

All together it sounds like too complex solution (2 languages, 3 parts...), so maybe one MDL application that will create the toolbox programmatically is better solution. The code itself will be simpler (because no need for Symbol provider) and more complex (because of code responsible for the toolbox itself).

BTW In MicroStation CONNECT Edition the discussed event monitoring issue is solved, because ribbon customization (not old toolboxes) allows to choose what MicroStation event (fixed pre-defined list) should trigger reevaluation of show/hide and enable/disable tests used in ribbon tools definitions.

With regards,

  Jan