[Bug] MAUI Blazor - Router AppAssembly could not find pages if assembly is different

[sencagri]

Description

I am building a blazor project which has a common razor library. WASM and Blazor server uses same project to serve pages and components. I have added a new MAUI Blazor project and referenced the library. Project builds and runs but Router couldn't find the pages. It just show a white blank screen. I am adding a sample project for reproducing.

Expected Behavior

It should run like Blazor Server and Blazor WASM.

Actual Behavior

Router can find MainLayout but cannot find the actual page.

Screenshots

MAUI Blazor - Not Working Blank Screen

Blazor WASM - Working

Blazor Server - Working

What I have tried

Reproduction Link

BlazorSharedProject.zip reproducing project

[rogihee]

You need to tell the Router that there are additional assemblies to scan for routes by setting the "AdditionalAssemblies" property, so something like:

AdditionalAssemblies="new[] { typeof(BigTextComponent).Assembly }" 

[sencagri]

I already tried that both with changing AppAssembly and adding my component assembly to AdditionalAssemblies. It didn't work.

[Eilon]

I just tried this with AdditionalAssemblies and it worked fine.

In my MAUI app project I have Main.razor with exactly this content:

<Router
    AppAssembly="@GetType().Assembly"
    PreferExactMatches="true"
    AdditionalAssemblies="new[]{typeof(MauiRazorClassLibrarySample.Component2).Assembly}"> @* <------- ADD THIS PROPERTY *@
    <Found Context="routeData">
        <RouteView RouteData="@routeData" />
    </Found>
    <NotFound>
        <h1>Not found</h1>
        <p>Sorry, there's nothing here.</p>
    </NotFound>
</Router>

And in some page in the main app I have this navigation link:

<a href="/page1">Page1</a>

And in my Razor Class Library (RCL) I have a file Component2.razor with exactly these contents:

@page "/page1"

<h3>Component2</h3>

@code {

}

And when I click the link, it correctly loads the page1 page defined in the RCL's Component2.razor file.

[sencagri]

It looks same as mine. But I will try it again asap.

[Eilon]

I think I found the difference. In your repro app the file BlazorShared.Native\Main.razor has the app assembly also listed as an AdditionalAssembly:

AdditionalAssemblies="new[]{GetType().Assembly, typeof(BlazorShared.Docs.Pages.Index).Assembly}">

If you change it to just this;

AdditionalAssemblies="new[]{typeof(BlazorShared.Docs.Pages.Index).Assembly}">

Then it should work.

[Eilon]

BTW there is actually a hidden exception that says something about a duplicate route, which makes sense, because the main assembly has everything duplicated, but unfortunately that hidden exception just makes Blazor fail to load.

So I think there are two unrelated bugs here:

1. Blazor should possibly have a specific error saying that an assembly is duplicated, or just allow it (by ignoring the duplicate)
2. The duplicate route error should be more visible to the user somehow

[sencagri]

Thank you so much! 8 Ara 2021 Çar 03:23 tarihinde Eilon Lipton ***@***.***> şunu yazdı:

…

I think I found the difference. In your repro app the file BlazorShared.Native\Main.razor has the app assembly also listed as an AdditionalAssembly: AdditionalAssemblies="new[]{GetType().Assembly, typeof(BlazorShared.Docs.Pages.Index).Assembly}"> If you change it to just this; AdditionalAssemblies="new[]{typeof(BlazorShared.Docs.Pages.Index).Assembly}"> Then it should work. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#3258 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AB4VERO26ERRIILFW33JPJDUP2QPTANCNFSM5HLOBDLQ> .

[Eilon]

I filed these issues:

• Blazor bug for how duplicated app assembly is treated: Duplicating Router.AppAssembly in AdditionalAssemblies causes confusing error aspnetcore#38882
• Improve Blazor Hybrid experience with invalid routes (possibly due to duplicated router assembly): Blazor startup errors for duplicate routes is hard to discover and debug #3695

But I think the specific issue in this bug is resolved, so I'm closing this out. Very interesting issue 😄