Blazor Fundamentals in ASP.NET Core
💡 Concept Name
Blazor
📘 Quick Intro
Blazor is a framework for building interactive web UIs using C# instead of JavaScript. It runs on WebAssembly (Blazor WebAssembly) or on the server (Blazor Server) and integrates deeply with ASP.NET Core.
🧠 Analogy / Short Story
Think of Blazor as a magician that lets C# do JavaScript's job in the browser. Instead of sending a juggler (JS), you send a trusted knight (C#) who already knows your kingdom (backend). Less training, more synergy.
🔧 Technical Explanation
Blazor lets you build web apps with C# and Razor. It has two models:
- Blazor WebAssembly (WASM): Runs entirely in the browser using WebAssembly. No server round-trips.
- Blazor Server: UI events are handled over SignalR from the server. Lightweight but requires constant connection.
It supports routing, dependency injection, layout, components, forms, and JavaScript interop.
🎯 Purpose & Use Case
- ✅ Build SPA (Single Page Apps) using C# only
- ✅ Share code between client and server
- ✅ Leverage existing .NET libraries on frontend
- ✅ Avoid JavaScript for most UI logic
- ✅ Integrate easily with ASP.NET Core backend
💻 Real Code Example
// Counter.razor
@page "/counter"
Counter
Current count: @count
@code {
private int count = 0;
private void IncrementCount() => count++;
}
Key Concept: UI is updated reactively using Razor + C#. No JS needed.
❓ Interview Q&A
Q1: What is Blazor?
A: A framework for building interactive UIs using C#.
Q2: What are the two hosting models?
A: Blazor WebAssembly and Blazor Server.
Q3: Which model supports offline use?
A: Blazor WebAssembly.
Q4: How does Blazor Server communicate?
A: Via SignalR for UI updates.
Q5: Can Blazor use DI?
A: Yes, via @inject or constructor injection.
Q6: Is JavaScript still usable?
A: Yes, through JS Interop when needed.
Q7: Can I build PWA with Blazor?
A: Yes, Blazor WASM supports PWA setup.
Q8: Is SEO better in Server model?
A: Yes, because rendering is server-side.
Q9: Does Blazor support routing?
A: Yes, using @page directive in components.
Q10: What is .razor file?
A: A Blazor component combining C# and HTML markup.
📝 MCQs
Q1: What language does Blazor use for frontend?
- A. JavaScript
- B. C#
- C. Python
- D. Ruby
Q2: Blazor WebAssembly runs on?
- A. Server only
- B. Electron
- C. Browser via WebAssembly
- D. Docker
Q3: Which protocol is used in Blazor Server for communication?
- A. HTTP
- B. SignalR
- C. gRPC
- D. WebHooks
Q4: Which directive is used to define route in Blazor?
- A. @route
- B. @page
- C. @url
- D. @bind
Q5: Can Blazor call JS code?
- A. Yes, using JSInterop
- B. No, only C# is supported
- C. Yes, but only on server
- D. Only for logging
💡 Bonus Insight
Blazor lets you share code between client and server seamlessly. With .NET MAUI and Blazor Hybrid, you can even build native desktop and mobile apps using the same Razor components!
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