Missing Stylesheet after navigating in .NET 8

[UweKeim]

Issue

After navigating away and back to a page, a call to Swal.FireAsync() shows an alert that has CSS missing.

• Here is a video showing the behavior.
• Here is the project that I used for the video and below screenshots.

Steps

I've created a new Blazor Web App with these configuration settings:

I then added

<PackageReference Include="CurrieTechnologies.Razor.SweetAlert2" Version="5.5.0" />

to my project's CSPROJ file, added

<script src="_content/CurrieTechnologies.Razor.SweetAlert2/sweetAlert2.min.js"></script>

right to the end before the </body> tag:

and added this to my "Program.cs":

builder.Services.AddSweetAlert2(options =>
{
	options.Theme = SweetAlertTheme.Dark;
	options.SetThemeForColorSchemePreference(ColorScheme.Light, SweetAlertTheme.Default);
	options.SetThemeForColorSchemePreference(ColorScheme.Dark, SweetAlertTheme.Dark);
});

Next, I created a simple button in "Home.razor":

<button @onclick="@(async ()=>await Swal.FireAsync("Test!"))">Test, klick!</button>

I've also changed @rendermode InteractiveServer on that page. The full source code of the page looks like this:

@page "/"
@rendermode InteractiveServer
@inject SweetAlertService Swal

<PageTitle>Home</PageTitle>

<h1>Hello, world!</h1>

Welcome to your new app.

<button @onclick="@(async ()=>await Swal.FireAsync("Test!"))">Test, klick!</button>

This results in this:

When I click the button, it shows this alert:

I can do this multiple times successfully.

Next, I navigate to another page:

And then I navigate back to the home page:

When I then click the button, the alert appears, but it seems to have no styling:

It is shown that the bottom left of the page.

It seems to work correctly (i.e. I can click the OK button to close the alert), but it looks wrong.

Expected behavior

I would expect that Razor.SweetAlert2 works every time, not just when I do not navigate.

Desktop

• OS: Windows 11 German, 64 bit
• Browser: Google Chrome Version 120.0.6099.71 (Offizieller Build) (64-Bit)

[Pvxtotal]

Any workaround? Same problem here...

[UweKeim]

It seems, that all my favorite Blazor library developers have shifted priorities away from .NET 8 Blazor 😭.

[filipe-augusto]

I have the same problem.

[Pvxtotal]

I found a workaround. This is because of the new Blazor SSR, it changes the way that JS is rendered.

You need to use PageScript: https://github.com/MackinnonBuck/blazor-page-script

Import the SweetAlert2 Script in the MainLayout like this: <PageScript Src="./_content/CurrieTechnologies.Razor.SweetAlert2/sweetAlert2.min.js" />

Set a RenderMode for HeadOutlet like this: <HeadOutlet @rendermode="new InteractiveAutoRenderMode(prerender: false)" />

With this trick everything should be working just fine.

This trick solved issues with all JS-based libraries I've imported.

Source: https://learn.microsoft.com/en-us/aspnet/core/blazor/javascript-interoperability/static-server-rendering?view=aspnetcore-8.0

[UweKeim]

In case anyone wonders: The NuGet package of PageScript is named "BlazorPageScript".

And you have to add this to "_Imports.razor":

...
@using BlazorPageScript
...

[UweKeim]

@Pvxtotal When doing your steps, I get an error:

InvalidOperationException: A component of type 'Microsoft.AspNetCore.Components.Web.HeadOutlet' has render mode 'InteractiveAutoRenderMode', but the required endpoints are not mapped on the server. When calling 'MapRazorComponents', add a call to 'AddInteractiveWebAssemblyRenderMode'. For example, 'builder.MapRazorComponents<...>.AddInteractiveWebAssemblyRenderMode()'

Could you please share some more code of your solution?

[Pvxtotal]

@UweKeim in your case use HeadOutlet like this: <HeadOutlet @rendermode="new InteractiveServerRenderMode(prerender: false)" />

[UweKeim]

Thanks, @Pvxtotal, I've already tried that, too, without success.

I've changed the <HeadOutlet /> in mit "App.razor" to:

<HeadOutlet @rendermode="new InteractiveServerRenderMode(prerender: false)" />

I removed this from the "App.razor":

<script src="_content/CurrieTechnologies.Razor.SweetAlert2/sweetAlert2.min.js"></script>

And then I've added this to "MainLayout.razor":

<HeadContent>
	<PageScript Src="_content/CurrieTechnologies.Razor.SweetAlert2/sweetAlert2.min.js" />
</HeadContent>

When clicking the button to show a SweetAlert2 dialog, I get this error:

Error: Microsoft.JSInterop.JSException: Could not find 'CurrieTechnologies.Razor.SweetAlert2.Fire' ('CurrieTechnologies' was undefined).

With this call stack:

Error: Could not find 'CurrieTechnologies.Razor.SweetAlert2.Fire' ('CurrieTechnologies' was undefined).
    at https://localhost:7133/_framework/blazor.web.js:1:734
    at Array.forEach (<anonymous>)
    at l.findFunction (https://localhost:7133/_framework/blazor.web.js:1:702)
    at b (https://localhost:7133/_framework/blazor.web.js:1:5445)
    at https://localhost:7133/_framework/blazor.web.js:1:3238
    at new Promise (<anonymous>)
    at y.beginInvokeJSFromDotNet (https://localhost:7133/_framework/blazor.web.js:1:3201)
    at fn._invokeClientMethod (https://localhost:7133/_framework/blazor.web.js:1:62541)
    at fn._processIncomingData (https://localhost:7133/_framework/blazor.web.js:1:60016)
    at connection.onreceive (https://localhost:7133/_framework/blazor.web.js:1:53657)
   at Microsoft.JSInterop.JSRuntime.InvokeAsync[TValue](Int64 targetInstanceId, String identifier, Object[] args)
   at CurrieTechnologies.Razor.SweetAlert2.SweetAlertService.FireAsync(String title, String message, SweetAlertIcon icon)
   at BlazorApp6.Components.Pages.Home.<BuildRenderTree>b__0_1() in C:\Users\ukeim\Documents\Visual Studio 2022\Projects\BlazorApp6\Components\Pages\Home.razor:line 11
   at Microsoft.AspNetCore.Components.ComponentBase.CallStateHasChangedOnAsyncCompletion(Task task)
   at Microsoft.AspNetCore.Components.RenderTree.Renderer.GetErrorHandledTask(Task taskToHandle, ComponentState owningComponentState)

Probably I'm missing something but can't figure out what.

[Pvxtotal]

@UweKeim  Change it to: <PageScript Src="./_content/CurrieTechnologies.Razor.SweetAlert2/sweetAlert2.min.js" />

./ at the start

[UweKeim]

Thanks again, @Pvxtotal, I've also tried this without success.

[UweKeim]

It seems that I solved it by not placing the <PageScript... component into the <HeadContent> tags, but simply at the very end of the "MainLayout.razor" page:

<PageScript Src="/_content/CurrieTechnologies.Razor.SweetAlert2/sweetAlert2.min.js" />

I still have to have this in the "App.razor":

<HeadOutlet @rendermode="new InteractiveServerRenderMode(prerender: false)" />

But all after all, it seems to work.

[Basaingeal]

Sorry for my absence. I'll be looking into this, but .NET 8 runtime support has been added. That may aleviate this issue, but if there is a breaking change in .NET 8 I'll need to work out a fix.

[Pvxtotal]

@Basaingeal This is related to how Blazor SSR load scripts when enhanced navigation is on. If you disable enhanced navigation everything works fine. I still don't know any workaround besides disabling enhanced navigation or turning the entire app into Interactive.

Source: dotnet/aspnetcore#52273