Introduction to Blazor

What is Blazor?

For years, building interactive web pages meant one thing: JavaScript. Whether you loved it or not, it was the only language browsers understood. That's no longer the case. Blazor is a web framework from Microsoft that lets developers build interactive user interfaces (UIs) using C# instead of JavaScript.

This means you can write your front-end logic in C#, use the powerful tools and libraries from the .NET ecosystem, and create modern, single-page applications (SPAs) without writing a single line of JavaScript. It works by allowing C# code to run either directly in the browser or on the server, giving you flexibility in how your app is delivered.

The Blazor Advantage

The biggest advantage of Blazor is using one language, C#, for both client-side and server-side code. This simplifies development for teams already familiar with .NET. You can share code, like data validation models, between the front-end and back-end, which reduces duplication and makes the application easier to maintain.

It also opens up the entire .NET library ecosystem for client-side development. Need to perform a complex calculation or process data in a specific way? You can use a trusted .NET library you already know, rather than searching for a JavaScript equivalent.

With Blazor, you can build a full-stack web application with just C# and .NET, creating a more consistent and productive development experience.

Building with Components

Like other modern web frameworks, Blazor is built around a component-based architecture. A component is a self-contained, reusable piece of the UI. It can be something small, like a button or a text input, or something large, like an entire user registration form or even a whole page.

These components are created using Razor syntax, a clean way to mix HTML markup with C# code. This allows you to define a component's structure, styling, and logic all in one place. A simple button component, for instance, would contain the HTML for the button and the C# code to handle what happens when it's clicked.

@page "/counter"

<h1>Counter</h1>

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

<button class="btn btn-primary" @onclick="IncrementCount">Click me</button>

@code {
    private int currentCount = 0;

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

In this example, the HTML creates the display, and the C# in the @code block manages the state and handles the button's click event. This blend of markup and logic makes building complex UIs intuitive.

Hosting Your App

Blazor offers two main ways to host your application: Blazor Server and Blazor WebAssembly. Choosing the right one depends on your project's needs.

Blazor Server apps run on the server. The browser acts as a thin client, and any user interactions are sent back to the server over a real-time connection using a technology called SignalR. The server processes the event, updates the UI, and sends the changes back to the browser.

Blazor WebAssembly (Wasm) apps run entirely in the user's browser. The application, its dependencies, and the .NET runtime are downloaded to the client on the first visit. After that, the app runs directly on the user's device, making it fast and capable of working offline.

Feature	Blazor Server	Blazor WebAssembly
Where Code Runs	Server	Client's Browser
Initial Load	Fast	Slower (downloads .NET runtime)
Responsiveness	Depends on network latency	Instant (runs locally)
Offline Support	No	Yes
Server Requirement	Requires an ASP.NET Core server	Can be hosted on a static file server

Ultimately, Blazor provides a powerful and flexible way for .NET developers to build modern web applications, whether they need a lightweight, server-rendered site or a rich, client-side application that can work offline.

C# Blazor Web Development