When creating a data form add-in with SDK , VB.net works OK , C# fails to create supplimentary files.
The c# class created is not a partial class , no CodeGen file crreated to give access to the fields and other components of the form. Therefore it is not possible to use the Data Form Add-in with C#
We are currently evaluating this issue and will update this article when we have more information.
Steps to Duplicate
Simply follow this short tutorial: https://www.blackbaud.com/files/support/guides/infinitydevguide/Subsystems/dataforms-developer-help/dataforms-developer-help.htm#Exercises/coexCreatingADataFormAddIn.htm%3FTocPath%3DMore%2520Data%2520Form%2520Samples%2520and%2520Exercises%7CStep%2520by%2520Step%2520Exercises%7C_____7
VB.net will behave exactly as the guide documents. Follow the same procedures using C# and you will be missing supplementary files as per the guide.