An Introduction to Blazor

What is Blazor ?

(this post is based on Blazor 0.3)

To make it easy : Blazor is just like vuejs / angular / reactjs … but you code in C# with the Razor syntax :)

Main notions

Blazor is articulated around the followings notions :

  • App Root (there is no official name for it) : mostly named “index.html”, it’s the first file loaded by the user and it will have the following content My root file
    • html minimal tags (html/header/body)
    • external reference : the js / css files you need from external providers (like jqueryui or toastr)
    • a root tag on which the pages will be rendered
    • a script tag for loading the blazor script
  • App.cshtml : temporary file for configuring your app (by default only the Router scanning is here) My App.cshtml
  • component : a razor template and it’s c# code that will manage a part of the page.
  • page : just like a component but it will be created on the application body when the user loads an url on its browser
  • interop functions : link you can create between a js function and a c# function (defined in this 2 files C# side and JS side
  • Entry point My File just like the program.cs in core app you define :
    • Dependency injection configuration
    • Framework specific settings (here I just set the name of the tag on the root App Root that’ll be replace by the page content).

You can view all these notions on my TOSS project Here

Visual Studio integration

You need at least Visual Studio 15.7 and the Blazor Language Service here. Visual Studio gives the following tools regarding Blazor :

  • 2 project templates
  • code coloration on pages/components
  • code autocompletion on pages/components
  • project building
  • with the already existing IIS Express integration you can host your project locally and test it on your dev computer.

How it works ? (or how I understand it works)

  • When you build, all the components / pages are translated to pure C# classes (you can find them on your project /obj folder)
    • All these classes have interaction with Microsoft.AspNetCore.Blazor.RenderTree.RenderTreeBuilder which is and html tag writer
    • When changes occurs on the view model of the component or page, the BuildRenderTree is called and then the content is updated
  • All these clases are the compiled for targeting .netstandard 2.0
  • When the browser loads index.html it loads blazor.js a library that will
    • load your project entry point
    • load it’s dependencies (all targeting .netstandard 2.0)
    • init web assembly if the browser doesn’t support it
    • load mono.wasm, an implementation of the platform working with Web Assembly (don’t ask me more yet, I’m trying to understand it as I learn Blazor), so your code and your dependencies can actually get executed on the brower and interact ith the dom


That’s it for now, in the next step I’ll go deeper on some of Blazor functionnalities or I’ll show how to implement some basic functionnaltiies like authentication or CSRF protection.