Blazor WebAssembly lazy loading assemblies not working when using @ref attribute in the component

[ajithr]

Describe the bug

• When using Blazor WebAssembly lazy loading assemblies with component's @ref attribute, the corresponding assembly could not load issue throws in the browser console and the application not running.

To Reproduce

https://github.com/ajithr/blazor-wasm-lazy-ref

• Check out the above repo and open ~/LazyLoadingRef/LazyLoadingRef.csproj file in the VS 2019.
• Run the application it will throw exceptions in the browser console.
• Open ~/LazyLoadingRef/Pages/Counter.razor file and remove @ref attribute and LazyLoadComponent reference in the @code section.
• Run the sample again and it will work properly with the lazy loading feature.
  

Exceptions (if any)

Further technical details

• ASP.NET Core version - .net5.0

• Include the output of dotnet --info
  

• The IDE (VS / VS Code/ VS4Mac) you're running on, and its version
  

[javiercn]

@ajithr thanks for contacting us.

This seems to be an issue, I can't tell there's anything wrong from looking at the code.

@captainsafia do you have any thoughts?

[ghost]

Thank you for contacting us. Due to a lack of activity on this discussion issue we're closing it in an effort to keep our backlog clean. If you believe there is a concern related to the ASP.NET Core framework, which hasn't been addressed yet, please file a new issue.

This issue will be locked after 30 more days of inactivity. If you still wish to discuss this subject after then, please create a new issue!

[ajithr]

@mkArtakMSFT @javiercn @captainsafia The issue is closed itself by msftbot. Do we really need to create a new issue report for this? It is not yet discussed and it is under investigation.

[captainsafia]

@ajithr Thanks for the following up. Reopening this issue and moving to backlog.

I had a hunch that this might be caused by some issues that existed in the codepaths used for assembly loading in the WASM runtime. We'll need to (1) validate if this still happens in .NET 6 and (2) investigate why if it does.

[ghost]

Thanks for contacting us.
We're moving this issue to the Next sprint planning milestone for future evaluation / consideration. We will evaluate the request when we are planning the work for the next milestone. To learn more about what to expect next and how this issue will be handled you can read more about our triage process here.

[guardrex]

@captainsafia ... My error from our offline chat is the same accessing a type in a lazily-loaded RCL assembly. Should I add my error details here or open a new issue?

[captainsafia]

@guardrex You can add the details here. Both issues might have the same root cause.

[guardrex]

Error:

crit: Microsoft.AspNetCore.Components.WebAssembly.Rendering.WebAssemblyRenderer[100]
Unhandled exception rendering component: Exception of type 'System.Reflection.ReflectionTypeLoadException' was thrown.
Could not load type of field 'LazyLoadTest.Pages.Robot+RobotModel:k__BackingField' (0) due to: Could not load file or assembly 'GrantImaharaRobotControls, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' or one of its dependencies.

The error isn't thrown when the user tries to navigate to the component: It's thrown at app start up.

The lazily-loaded RCL assembly (GrantImaharaRobotControls.dll) includes:

public enum Axis
{ 
    Left,
    Right,
}

The WASM app seeks to use the type in a component (Pages/Robot.razor in the app) ...

@page "/robot"
@using GrantImaharaRobotControls

...

@code {
    private RobotModel robotModel = new() { AxisSelection = Axis.Left };
    
    ...

    public class RobotModel
    {
        public Axis AxisSelection { get; set; }
    }
}

In App.razor ...

if (args.Path.EndsWith("/robot"))
{
    var assemblies = await AssemblyLoader.LoadAssembliesAsync(new[] { "GrantImaharaRobotControls.dll" });
    lazyLoadedAssemblies.AddRange(assemblies);
}

In the project file ...

<ItemGroup>
  <BlazorWebAssemblyLazyLoad Include="GrantImaharaRobotControls.dll" />
</ItemGroup>

Repro project: https://github.com/guardrex/LazyLoadSolution

To workaround this for the doc, I've simply placed the Robot component into the RCL. It's routable from the app, renders fine, and uses Axis fine in the RCL. We can go with that for the doc. I cross-link to this engineering issue from a remark in the topic. I'll revert/version and/or update the doc remark later. I plan to shoot that PR in shortly ... tomorrow maybe. dotnet/AspNetCore.Docs#22603

[ghost]

We've moved this issue to the Backlog milestone. This means that it is not going to be worked on for the coming release. We will reassess the backlog following the current release and consider this item at that time. To learn more about our issue management process and to have better expectation regarding different types of issues you can read our Triage Process.

[Bala-E98]

Hi Guys,
I'm facing same exceptions. May I know the status of this issue?

[Sureshv2]

Hi Guys

Because of @ref attribute issue, we cannot use lazy loading assembly feature in our project and it is downloading all referenced assemblies which is not required at initial startup page. Please do let us know that when it could be fixed.

[bingxueyinlian]

same problem

[syncsiva]

Hi Guys, Any update on this issue. This affects using Lazy loading in blazor WASM apps.

[laurence73]

same problem

[ghost]

Thanks for contacting us.

We're moving this issue to the .NET 8 Planning milestone for future evaluation / consideration. We would like to keep this around to collect more feedback, which can help us with prioritizing this work. We will re-evaluate this issue, during our next planning meeting(s).
If we later determine, that the issue has no community involvement, or it's very rare and low-impact issue, we will close it - so that the team can focus on more important and high impact issues.
To learn more about what to expect next and how this issue will be handled you can read more about our triage process here.

[ghost]

We've moved this issue to the Backlog milestone. This means that it is not going to be worked on for the coming release. We will reassess the backlog following the current release and consider this item at that time. To learn more about our issue management process and to have better expectation regarding different types of issues you can read our Triage Process.

[danroth27]

Both repro projects seem to work fine with .NET 7, so it looks like this issue is now fixed. If you're still hitting this issue, please let us know and provide detailed steps to reproduce the problem and we'll take another look.