Having developed a well working ASP.NET Core App (which runs in a Kubernetes Cluster), I have the offer to develop an additional functionality. This functionality should only be available for this customer. Not the other customers. So I was thinking if I could develop this functionality as a "Plugin" for my App.

But unfortunately I never did this before and googling it led to more confusion than clarification.

I mean, I can think about adding a function as separate DLL, which seems to be a common practice. But how do I tell my app, that having this plugin, it has to behave differently?

For example, my plugin will create a Button on the Main Site with an according clicking-method behind. How does my Code has to look like in the index.cshtml file and in the Controller and in the JavaScript file?

Hope you understand what I mean, if not, please ask right away. Thank you for the answers in advance.