Blazor vs React: A .NET Developer's Honest Comparison

Source: Dev.to

What Is Blazor, Anyway?

Blazor is Microsoft’s framework for building interactive web UIs using C# instead of JavaScript. The name is a portmanteau of Browser and Razor (the .NET templating syntax), and it’s been production‑ready since 2020.

The core idea is that you write C# that either:

• Runs on the server (Blazor Server) – Your C# executes on the server, and UI updates flow to the browser via a SignalR WebSocket connection in real‑time.
• Runs in the browser (Blazor WebAssembly) – The .NET runtime itself runs in the browser via WebAssembly. Yes, actual compiled .NET code, in your browser.
• Both (Blazor United/.NET 8+) – Pick your rendering mode per component. Server‑side for initial‑load speed, WebAssembly for offline capability. Best of both worlds.

// A Blazor component. Yes, that's C# in your UI.
@page "/counter"

<h2>Counter</h2>

<p>Current count: @currentCount</p>

<button @onclick="IncrementCount">Click me</button>

@code {
    private int currentCount = 0;

    private void IncrementCount()
    {
        currentCount++;
    }
}

That’s it. No webpack. No Babel. No dozens of configuration files. Just C# that compiles and runs.

The Case Against React

React is fine. It revolutionized component‑based UIs, and the Virtual DOM was genuinely clever. Facebook uses it, and they seem to be doing okay.

However, after years of building production React applications, I started noticing patterns that made me question my life choices:

• Ever‑shifting ecosystem – Every year a new “right way” to do things emerges.

• Tool overload – Starting a new React project means choosing from dozens of bundlers, state‑management libraries, styling solutions, data‑fetching tools, form libraries, and meta‑frameworks before writing any business logic.

• TypeScript limitations – TypeScript is a band‑aid on a dynamically‑typed language. Types are only compile‑time suggestions; runtime validation is still manual.

// TypeScript: Types are suggestions, really
const user: User = JSON.parse(response); // No runtime validation!

// Meanwhile, in C#:
var user = JsonSerializer.Deserialize(response); // Actual deserialization with type checking

• Security liability of node_modules – Large dependency trees and a volunteer‑maintainer model make the npm ecosystem prone to supply‑chain attacks.

The Greatest Hits of npm Disasters

Why this keeps happening

• Massive dependency trees – a typical React app has hundreds of transitive dependencies, each an attack surface.
• Volunteer maintainers – critical infrastructure is often maintained by unpaid individuals who can be phished or socially engineered.
• No build‑time verification – npm installs whatever package.json says without compile‑time safety checks.
• Trivial packages – the ecosystem normalizes depending on tiny utilities (is‑odd?, is‑even?) that collectively add up to a huge attack surface.

A real npm audit from a “simple” React project:

found 47 vulnerabilities (12 moderate, 28 high, 7 critical)

Code Comparison: React vs Blazor

React (with hooks)

import { useState } from 'react';

export default function Counter() {
  const [count, setCount] = useState(0);

  return (
    <div>
      <h2>Counter</h2>
      <p>Current count: {count}</p>
      <button onClick={() => setCount(count + 1)}>Click me</button>
    </div>
  );
}

Blazor

@page "/counter"

<h2>Counter</h2>

<p>Current count: @count</p>

<button @onclick="() => count++">Click me</button>

@code {
    private int count = 0;
}

Both examples are similar in line count, but the Blazor version has no imports, no useState hook, and no separate setter function—just a plain variable and an increment.

Why Blazor Works for Me

• Zero npm audit nightmares – dotnet list package --vulnerable usually returns zero results.
• Signed packages – NuGet packages can be cryptographically signed.
• Curated ecosystem – Fewer packages overall, but higher average quality.
• Microsoft backing – Core libraries are maintained by a trillion‑dollar company, not solo developers.
• Compile‑time safety – The C# compiler catches many issues before runtime.
• Smaller dependency graphs – .NET’s comprehensive standard library reduces the need for external packages.

Blazor’s Evolution: .NET 8, 9, 10

• .NET 8 introduced Blazor United, allowing per‑component rendering mode selection (Server vs WebAssembly).
• .NET 9 added improved Hot Reload for faster UI iteration.
• .NET 10 (preview) promises tighter integration with MAUI and native‑like performance for WebAssembly.

When React Still Makes Sense

• Projects that require massive existing JavaScript ecosystems or third‑party React components not yet ported to Blazor.
• Teams with deep JavaScript expertise and limited C# experience.
• Scenarios where client‑side only rendering is mandatory and the overhead of a .NET runtime in the browser is unacceptable.

Getting Started with Blazor

1. Install the .NET SDK (≥ 8.0).

2. Create a new project:

   dotnet new blazorwasm -o MyBlazorApp

3. Run the app:

   cd MyBlazorApp
   dotnet run

4. Open https://localhost:5001 in your browser and explore the default template.

5. Add a new page by creating a .razor file (e.g., Counter.razor) and follow the component pattern shown earlier.

FAQ: Common Concerns Answered

Q: Do I need to learn Razor syntax?
A: Yes, but it’s a natural extension of HTML with C# code blocks. The learning curve is shallow for anyone familiar with C#.

Q: How does performance compare?
A: Blazor WebAssembly startup is slightly slower than a pure JS bundle, but once loaded, runtime performance is comparable. Blazor Server offers near‑instant UI updates with minimal client payload.

Q: Can I use existing JavaScript libraries?
A: Absolutely. Blazor provides JavaScript interop (IJSRuntime) to call into any JS library when needed.

Q: What about SEO?
A: Server‑side rendering (Blazor Server or pre‑rendered WebAssembly) delivers fully rendered HTML to crawlers, improving SEO.

Final Thoughts

Switching from React to Blazor gave me a single‑language stack, dramatically reduced dependency‑related security headaches, and simplified the development workflow. React remains a powerful tool, especially when you’re locked into a JavaScript‑centric ecosystem, but for .NET developers seeking tighter integration, compile‑time safety, and a more predictable dependency graph, Blazor is a compelling alternative.