Creating Custom action using .net api

I am currently faced with the task of creating an account (company record) from a person record in Sage 200 CRM 7.3. The mappings are defined in a custom entity.

Coming from a mvc background, I was thinking about creating a c# class with a method in it to create the company record. The method would receive the person id.

Is using the .net api the correct approach for this and, if so, please can someone advise me what project type I need to create and what dlls I need to reference.

Many Thanks