Simple demo for using .NET code generators to enforce project- or team- specific code quality standards.

General usage pattern:

• Define .NET attributes for your code quality rules
• Apply those attributes to the classes/methods/interfaces that you want enforced
• Write custom code generators that scan for those attributes and add warnings/errors whenever the underlying code quality standards are broken

Benefits:

• These warnings/errors are treated by the IDE or build tool just like regular compilation warnings/errors.
• The logic behind them is 100% specific to your team/project, can be easily viewed and changed and is fully customizable.
• No third-party dependencies of any kind are needed (other than those for code generators).

Some of the things that can be enforced this way (in order of complexity):

• Ensure that some parts of the code (e.g. business logic methods, services) don't exceed a certain complexity, in terms of nesting, total number of statements, expression complexity, etc.
• Ensure that public-facing APIs/endpoints only return DTO objects marked as such
• Ensure that certain code structure rules are followed (e.g. certain enums, the interfaces that use them and their implementations all follow specific namespace rules)
• Ensure that very specific coding rules are followed, e.g. that every method that works with an instance of a certain interface calls a specific method on that interface before returning, on all code paths.
• Since this is a generator, it can also emit code to enforce rules at runtime, e.g. by wrapping any given service, by injecting initialization code, etc.

Project structure:

Project	Purpose
Common	Common code between the generator and the actual project code. Contains the attributes and other things needed to describe the rules to be enforced.
CodeGeneratorEnforcer	The actual project codebase, to be enforced by the generator.
ActualGenerator	The generator project that does the actual enforcing

Things to pay a bit more attention to:

• The .csproj files. Linking the three projects together PROPERLY is not difficult, but does require a bit of trial and error. Comments in the .csproj files have been left to help with this.
• Debugging is not quite user friendly or intuitive, the best way to do it is via code in the Initialize() method.