What should i do to create Custom code validator according to my sdk in visual studio

Question

I have never developed visual studio extensions. I don't know what should I do create custom validator that will validate code written in c# using my dll, whether they confirm to certain criteria.

For example, I have a class like this:

public class ReturnMessage<T> where T : new()
{
    public void SetSuccess(string message, T value)
    {}
}

I would like to check if this class is being used to return response, then SetSuccess method should be called before return is sent.

Any directions, for starters would of great help as I don't what should be ideally done to achieve this.