Here is a great example that came up last week. Almost exactly like the OP. (It is even an onclick!)
I have a C# .net MVC web project. All of the JS, .cshtml templates and C# controllers are in the same visual studio solution. So it has complete vision into the code.
So the boundary is from cshtml template to javascript function and then another one from the js function (ajax call) to C# controller.
Visual studio has complete vision, but loses the connection at each boundary, so intellisense says that the C# controller function is never called.
I am not criticizing Visual Studio, it is a great tool, but this is a hard problem.
