I roughly know how to make a mvc uml class diagram en can find enough info/ examples on the internet. The only thing i cant find info about is if it makes a difference when you have a jacascript controller/model and a c# controller/model.
In general: no. UML is technology independent. Most models don't assume the technology. MVC can also be applied to different programming languages.
You only need to be aware that there are some concepts that are not handled by particular languages. The only thing that comes to my mind here is multiinheritance. Just use interfaces instead of (eventual) multiinheritance and there'll be no problem.
I can also imagine that some details can be designed in different ways to achieve better performance, but you'd need to know both languages perfectly to be able to make such decisions.
So don't bother about specific language and your diagram will be fine.