BlazorScopedCss is a library to fill the css gap in current Blazor version. This is how it works:

1. Dependency Injection time: go to Startup.cs ConfigureServices and add the line bellow: services.AddBlazorScopedCss(Assembly.GetExecutingAssembly());

2. Go to the main cshtml or html file and add the <style id="scopedCss"></style tag inside html->head, this is the place where BlazorScopedCss will render the styles

3. In the same file, add the BlazorScopedCss js: <script src="/_content/BlazorScopedCss/jsInterop.js"></script>

4. Time to add the css! In the folder where your component or page is located, add the css file, FetchData.razor.css for example (Visual Studio will nest the file inside .razor, awesome!)

5. Inside de CSS, add some classes:

.myFirstScopedComponent-scopeId {
    background-color: red;
}

.mySecondScopedComponent-scopeId {
    background-color: blue;
}

This library will replace -scopeId by the componentId, so...if you don't put this keyword it will not work!

6. Select the css in solution explorer and press f4 (properties), change the Build Action to Embedded resource

7. Ok, now go to your .razor page or component, and add BazorScopedCss:

<BlazorScopedCss.ScopedStyle EmbeddedStylePath="FetchData.razor.css"
                             Parent="this"
                             AfterInit="StateHasChanged"
                             @ref="scopedStyle" />

@if (scopedStyle?.IsComplete ?? false)
{
    <h1 class="@scopedStyle.CssScopedClasses(scopedCssClasses: "myFirstScopedComponent")">Weather forecast</h1>

    <p class="@scopedStyle.CssClassesMixed(nonScopedCssClasses: "display-1", scopedCssClasses: "mySecondScopedComponent")">This component demonstrates fetching data from a service.</p>
}

That's it! Watch HTML <style id="scopedCss"> tag to see the magic :)

https://www.nuget.org/packages/BlazorScopedCss