Assembly lazy load in a Blazor WebProject with rendermode InteractiveWebAssembly(Page/component)

[GLuca74]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

Hello,

following this example:
https://learn.microsoft.com/en-us/aspnet/core/blazor/webassembly-lazy-load-assemblies?view=aspnetcore-8.0

I was able to use the assembly lazy load in a Blazor WebAssembly application in net8, now I am trying to implement the same in a Blazor Web Application with rendermode InteractiveWebAssembly.
The start solution has two project, the application project and the .Client project. I added a RCL library (LazyLibrary) to the solution, inside the RCL I added a page component with @rendermode RenderMode.InteractiveWebAssembly. I added to .Client project a reference to RCL and I added

<ItemGroup>
  <BlazorWebAssemblyLazyLoad Include="LazyLibrary.wasm" />
</ItemGroup>

to application project file, but I can not navigate to the page in the RCL.
This are the key points I understood:
The classic Blazor WebAssembly project has Router.AdditionalAssemblies empty when it starts. The Blazor webApp seems always ignore Router.AdditionalAssemblies but use the new extension method app.MapRazorComponents<App>().AddAdditionalAssemblies(...), so to reproduce the same I didnt add the LazyLibrary to AddAdditionalAssemblies. In this case, when I run the applicazion and I try to navigate to the page in the RCL, I get a 404 and OnNavigateAsync not fire. So I tried to add the LazyLibrary to AddAdditionalAssemblies in programs.cs. In this way, when I navigate to the page in the RCL, the body of the page is rendered, OnNavigateAsync fire, but I get the error:

If i first navigate to counter(that download the application) and after I navigate to the page in the RCL I get this error

Maybe because the asemblies added (in OnNavigateAsync) to Router.AdditionalAssemblies is ignored.

So is it possible implement Assembly lazy load in a Blazor Web project with rendermode InteractiveWebAssembly?

If it is useful the simply project I am using is at :
https://github.com/GLuca74/BlazorApp2

Thanks

Expected Behavior

Implement Assembly lazy load

Steps To Reproduce

https://github.com/GLuca74/BlazorApp2

Exceptions (if any)

No response

.NET Version

8.0.107

Anything else?

No response

[gilm0079]

I've been battling with this for 2 days now. I thought I was going crazy as I'm not finding anything else online that shows I'm doing something wrong. I just found this issue and it is exactly what I'm having issues with. I've been working to convert our .net7 project to .net8. This lazy loading worked great in .net7. It does not work in .net8 when you start using the Render Modes structure.

My sample app also uses Page/component defined render modes. I have an RCL project with a razor component page. If the render mode on the page is InteractiveServer it works as it finds the assembly on the server. If I use auto or webassembly render modes it does not work. My solution uses the new structure of the App.razor and Routes.razor in the "server" project. The "server" project program.cs puts the RCL in the AddAdditionalAssemblies of the MapRazorComponents so that blazor routing can register the page. The RCL assembly is set in BlazorWebAssemblyLazyLoad.

The OnNavigatingAsync runs on the route change and shows successfully registering the lazy assembly. The RCL assembly never shows up in the browser application cache with the rest of the _framework wasm files. When LazyAssemblyLoader.LoadAssembliesAsync runs it never makes a network call to get the _framework wasm file. Before that fetch method runs I checked OperatingSystem.IsBrowser() and it is false. I'm assuming this is the problem. The router is running in a server context and loads the assembly from the server. In .net7 there wasn't this hybrid render modes so the router was running inside of the client wasm project and executing the route change handler in the browser context.

Is this a bug in how Blazor8 is supposed to work between server/browser to ensure wasm libraries as synchronized? Or is this a project structure bug? Every mention I see of Blazor 8 says the Router now exists in the server project which is different for me coming from .net7 blazor. I don't see how the router could be moved back to the client project anyway because the Router needs a reference to the AppAssembly which is now in the server project. Please advise.