[MVUX / Navigation] Update ViewModelMappings

[dr1rrb]

What would you like to be added:

Improve the way ViewModelMappings is being generated.

Why is this needed:

1. We are generating them in the "assembly name" namespace,
   • This can be confusing
   • When generating it from the head project, it forces user to use #pragma code
2. There is no way to easily merge mappings from multiple projects
3. Users have to explicitly reference generated code

Proposed solution

Following the KeyPropety generator, we can generate some internal types that will register mappings to a static registry using [ModuleInitializer] attribute.

For which Platform:

• [x] iOS
• [x] Android
• [x] WebAssembly
• [x] WebAssembly renders for Xamarin.Forms
• [x] Windows
• [ ] Build tasks

[nickrandolph]

@dr1rrb is work still required on this?

[VincentH-Net]

Question: will this issue fix also resolve below (found today in latest stable Uno 5 with Uno.Extensions.* 3.0.11)?

Page datacontext is set to TModel instead of bindable viewmodel after NavigateViewModelAsync<TModel>() when TModel is not defined in the same assembly as where it was registered in views/routes

Workaround: register bindable model instead of model in app views and routes (as indicated in point 3 in the issue description)

If not, I will register a separate issue

[dr1rrb]

Hey @VincentH-Net, yes the issue you have refers to the point 2 (which leads you to point 3 :) ).

And yes @nickrandolph the issue is still relevant :)

[agneszitte]

@dr1rrb, @nickrandolph I imagine this issue is still relevant?