Blazor Architecture & Enterprise Patterns
Lesson 4 of 30 13% of course

The Razor Syntax: Components, Directives, and Code-behind

14 · 8 min · 5/23/2026

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Mastering Razor

Razor is the templating engine that mixes HTML with C#. Understanding its nuances is key to building performant UIs.

1. Directives

- @page: Defines the URL route for the component.
- @inject: Injects a service from the DI container.
- @using: Imports namespaces.
- @implements: Specifies an interface implementation (like IDisposable).

2. Code-Behind Pattern

For small components, using <code>...</code> blocks inside the .razor file is fine. For large, complex components, use the **Partial Class** pattern. Create a MyComponent.razor.cs file. This keeps your HTML separate from your logic and makes the code much easier to manage and test.

3. Architect Insight

Q: "Should I use @bind or @onchange?"

Architect Answer: "Use @bind for simple two-way data binding. Use @onchange when you need to perform logic (like validation or an API call) immediately after the user changes a value. Remember: @bind is just syntactic sugar for a property and an event—don't be afraid to write it out manually if you need more control."

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Blazor Architecture & Enterprise Patterns

On this page

1. Directives 2. Code-Behind Pattern 3. Architect Insight
1. Blazor Foundations
Blazor Unleashed: The future of .NET Web development Hosting Models: Server-side vs WASM vs Auto (United) Project Structure: Proper layout for large-scale systems The Razor Syntax: Components, Directives, and Code-behind
2. Component Architecture
Component Communication: Parameters, EventCallbacks, and CascadingValues Render Fragments & Templated Components Custom Component Libraries: Building for reuse Error Boundaries: Graceful failure handling in UI
3. Data & State Management
Fluxor vs Simple State: Handling global state in Blazor Optimistic UI Updates and Data Persistence Handling Large Datasets: Pagination and Virtualization LocalStorage vs SessionStorage in WASM
4. SignalR & Interactivity
Blazor Server Hub: How it works under the hood JS Interop: Calling JavaScript from C# and vice versa SignalR Connection Resiliency and Circuit management Building Real-time Interactive Components
5. Security & Data Protection
Authentication State Provider: Custom Auth logic Securing APIs: JWT and Managed Identity in Blazor Role-based and Policy-based UI visibility Preventing XSS and CSRF in Blazor apps
6. Advanced Performance
Prerendering: Improving SEO and Initial Load time AOT (Ahead-of-Time) Compilation for WASM performance Lazy Loading Assemblies to reduce bundle size Memory Management and Leak prevention in WASM
7. Testing & CI/CD
Unit Testing Components with bUnit Integration Testing with Playwright and Blazor Mocking Services and JS Interop in tests Automating Blazor Deployments to Azure/AWS
8. The Blazor Architect's Case Study
Migrating an legacy WebForms/Silverlight app to Blazor Building a high-scale Enterprise Dashboard with Blazor