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im-ashar/reactiveblazor

22JavaScriptAudience · developerComplexity · 3/5Setup · moderate

TLDR

A .NET Blazor library that adds interactive, stateful UI components to server-rendered pages without requiring SignalR or WebAssembly, just C# with built-in CSRF protection and anti-replay security.

Mindmap

mindmap
  root((reactiveblazor))
    What it does
      Server-side interactivity
      No SignalR needed
      No WebAssembly needed
    How it works
      Server roundtrip on action
      DOM patching via Idiomorph
      Reactive Signals
    Tech Stack
      C# .NET
      Blazor
      Idiomorph
      Vanilla JavaScript
    Security
      Encrypted signed state
      CSRF protection
      Anti-replay tokens
    Use Cases
      Interactive forms
      Multi-component sync
      Stateful pages
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Things people build with this

USE CASE 1

Add interactive buttons and forms to a Blazor static server-rendered page without setting up SignalR or WebAssembly.

USE CASE 2

Keep multiple components on the same page in sync using typed Reactive Signals when one component's state changes.

USE CASE 3

Build a shopping cart where adding a product automatically updates a cart total component elsewhere on the same page.

USE CASE 4

Replace full-page reload form submissions with lightweight server-roundtrip updates that preserve scroll and cursor position.

Tech stack

C#.NETBlazorJavaScriptIdiomorph

Getting it running

Difficulty · moderate Time to first run · 30min

Requires .NET 8, 9, or 10 and existing familiarity with Blazor static server-side rendering.

No license information is mentioned in this explanation.

In plain English

ReactiveBlazor is a library for the .NET web framework Blazor that lets developers add interactive, stateful components to server-rendered pages without needing SignalR (a real-time connection protocol) or WebAssembly (code that runs inside the browser). Blazor's standard static server-side rendering mode does not support interactivity by itself, meaning buttons and form inputs do not respond to user actions without a full page reload. ReactiveBlazor fills that gap. When a user clicks a button or changes a form field on a ReactiveBlazor page, the browser sends a request to the server, the server updates the component's state and re-renders just that component, and the result is sent back and patched into the page without reloading. The patching uses a library called Idiomorph, which preserves scroll position, text cursor position, and CSS transitions during the update. The library handles a range of practical concerns automatically. Component state is encrypted and signed to prevent tampering, tokens expire after 24 hours by default, and anti-replay protection prevents a request from being submitted twice. CSRF protection is built in. Rapid interactions from the same component are queued to avoid race conditions. One notable feature is out-of-band updates via what the library calls Reactive Signals. One component can publish a typed signal (for example, a CartChanged signal when a product is added to a cart), and any other component on the same page that has declared interest in that signal is also re-rendered in the same server response. This keeps multiple components in sync without shared services or any custom JavaScript. The library supports .NET 8, 9, and 10, and bundles about 220 lines of vanilla JavaScript internally. Developers write no JavaScript of their own, all interaction logic lives in C#.

Copy-paste prompts

Prompt 1
I'm using .NET Blazor static server-side rendering. Show me how to install ReactiveBlazor and create a button that increments a counter on the server without a full page reload.
Prompt 2
Using ReactiveBlazor Reactive Signals, show me how to publish a CartChanged signal from a product component and have a cart summary component on the same page re-render automatically.
Prompt 3
How does ReactiveBlazor handle CSRF protection and state token expiration? Show me the relevant configuration options for .NET 9.
Prompt 4
Walk me through a minimal ReactiveBlazor form that validates user input on the server and shows an error message without reloading the page.
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