Blazor WebAssembly is GA: Everything You Need to Know

May 2020 marks the long-awaited General Availability of Blazor WebAssembly. This release allows C# developers to build Single Page Applications (SPAs) that run entirely in the browser using standard web technologies—no plugins required. We explore the trimming (linker) improvements and the architecture of a production-ready Blazor Wasm app.

The Download Size Challenge

Running .NET in the browser requires shipping the runtime. The IL Linker (Trace-based tree shaking) is crucial.

• **Debug Build**: ~10MB (Includes full symbols and assemblies).
• **Release Build**: ~1.8MB (Unused code stripped out, Brotli compressed).

<PropertyGroup>
    <BlazorEnableCompression>true</BlazorEnableCompression>
    <!-- Aggressive trimming -->
    <PublishTrimmed>true</PublishTrimmed>
</PropertyGroup>

Lazy Loading Assemblies

For large apps, verify the route before downloading the DLL.

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

@inject LazyAssemblyLoader AssemblyLoader

@code {
    protected override async Task OnNavigateAsync(NavigationContext context)
    {
        if (context.Path == "admin")
        {
            await AssemblyLoader.LoadAssembliesAsync(new[] { "AdminDashboard.dll" });
        }
    }
}

Key Takeaways

• Release builds are mandatory for performance testing.
• Lazy Loading significantly improves Time to Interactive (TTI).
• Use PWA capabilities to cache the runtime for repeat visits.