Why Blazor?
Silverlight was Microsoft’s attempt to bring .NET to the browser via a plugin. It failed because the web moved to open standards (HTML5). Blazor WebAssembly fulfills the original promise of Silverlight: running C# in the browser, natively, without plugins.
Technical Deep Dive
1. The “WCF RIA Services” Problem
This is the biggest blocker. WCF RIA Services automagically handled validation, serialization, and CRUD operations.
- Migration: You must replace this with ASP.NET Core Web API.
- Tip: Use gRPC if you need high-performance, strongly-typed contracts between client and server, similar to the old WCF experience.
2. UI Rewrite: XAML to Razor
You cannot copy-paste XAML to Blazor.
- Silverlight:
<Button Content="Click Me" Click="Button_Click" /> - Blazor:
<button @onclick="Button_Click">Click Me</button> - Strategy: Don’t just port the UI. Silverlight apps often look like Windows 98. Use this opportunity to implement a modern Design System (e.g., MudBlazor or Fluent UI).
3. Blazor Hosting Models
- Blazor WebAssembly (WASM): Runs entirely in the client browser. Best for offline support and low latency UI. Closest to Silverlight architecture.
- Blazor Server: Runs on the server, sends UI updates via SignalR. Best for apps with heavy proprietary algorithms you don’t want to download to the client.
Migration Complexity by App Type
Simple Apps (Forms, CRUD):
- ✅ XAML → Razor conversion is straightforward
- ✅ MVVM patterns transfer directly
- ✅ Most migrations succeed in 3-6 months
Complex Apps (Charts, Real-time Data):
- ⚠️ Blazor’s rendering performance is weaker than Silverlight
- ⚠️ Third-party chart libraries (Telerik, Syncfusion) are expensive
- ⚠️ Real-time SignalR can introduce latency
The Hidden Benefit
Blazor is great for internal enterprise apps because:
- ✅ No JavaScript fatigue (use C# for everything)
- ✅ .NET shops can reuse backend developers
- ✅ Strong tooling (Visual Studio, Rider)
Architecture Transformation
graph TD
subgraph "Legacy Silverlight"
A[Browser Plugin] --> B[WCF RIA Services]
B --> C[EDMX / EF Legacy]
C --> D[Database]
end
subgraph "Modern Blazor"
E[Blazor WASM] --> F[ASP.NET Core Web API]
F --> G[EF Core]
G --> D
E -.SignalR (Optional).-> F
end
style A fill:#f9f,stroke:#333,stroke-width:2px
style E fill:#bbf,stroke:#333,stroke-width:2pxPost-Migration: Best Practices
Months 1-3: Performance Tuning
- WASM Size: Optimize the download size of the Blazor app (Tree Shaking).
- Lazy Loading: Load assemblies only when needed to speed up initial load.
Months 4-6: Modernization
- PWA: Turn the Blazor app into a Progressive Web App (PWA) for installability.
- Design System: Implement a consistent design language across all internal tools.