Our "Simple" language sample in the sample project shows a relatively small implementation of a language that can do lexing, semantic parsing, AST building, and automated IntelliPrompt. That is a good reference for how to build such functionality.
This page also describes the general steps we implemented for the .NET add-on to achieve those features:
The .NET add-on isn't currently designed to be openly accessible for other languages. Also since the C# lexer for it is programmatic (written in code), you can tweak some things but others would require a new implementation of it. Your best bet if you want to reuse pieces of the add-on for a custom c++.NET language would be to purchase the add-on and its Blueprint source code. Then you can take out the bits and pieces of what you need to make it work.
As we move forward with development of our next gen SyntaxEditor framework (being prototyped with the WPF version), one plan is to make a lot of the core .NET add-on internals more accessible for people like you who wish to reuse logic we've written. However it will be a while yet before we are at a point where can do that.