Based on the information that you look for a solid body I assume that by "active document" you mean a Part document.
I can think of two ways to accomplish this:
Check if the volume of the model is zero
Check if there are any Edgebar features that create a volume (extrusions, party copies, etc.)
If by "empty" you also mean other part features like constructions, then forget solution 1) and extend the list of features in solution 2) accordingly.
i am planning to implement the button in assembly, part, weldment and sheetmetal.
With empt I mean no solid body (no volume)
I need a 3d printable object, so a 3D model, not just planes.
Thanks, I will get into that. I am also thinking about saving the model as a stl file and check if the stl filesize is greater than 0..
For part and sheetmetal documents, you should iterate through all Model objects in the Models collection and check for the Body.IsSolid property. If there is no solid body in any of the models, it is EMPTY.
For assembly documents, you will iterate through all its child documents and do the above check for part and sheetmetal occurrences. For subassemblies, you will iterate recursively. You have to stop the recursion as soon as you have found a solid body to tell that the assembly is NOT EMPTY.
For weldments, I don't know, but I think it's similar to the assembly documents.