Blazor WebAssembly Deep Dive

Published on September 14, 2025 by Jane Doe

Introduction

Blazor WebAssembly (WASM) lets you run .NET code directly in the browser without plugins. This post explores the inner workings, providing guidance to harness its full potential.

Architecture Overview

At a high level, a Blazor WASM app consists of:

• HTML shell (index.html)
• Mono runtime compiled to WebAssembly
• .NET assemblies (DLLs) loaded at runtime
• JavaScript interop layer

Boot Process

The boot sequence involves loading blazor.boot.json, initializing the Mono runtime, and rendering the root component.

// blazor.boot.json snippet
{
  "runtimeVersion": "7.0.10",
  "assemblyRoot": "_framework/",
  "assemblies": [
    "MyApp.dll",
    "Microsoft.AspNetCore.Components.Web.dll"
  ]
}
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Routing & Navigation

Routing is handled by the Router component which matches the URL to a Razor component.

@page "/counter"
@using Microsoft.AspNetCore.Components

Counter
Current count: @currentCount
Click me

@code {
    private int currentCount = 0;
    void IncrementCount() => currentCount++;
}
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Performance Tips

• Enable PublishTrimmed to reduce payload size.
• Use Lazy loading for large components.
• Compress static assets with Brotli/Gzip.

JavaScript Interop

Interop allows .NET to call JS and vice‑versa. Example:

// C#
await JS.InvokeVoidAsync("navigator.clipboard.writeText", text);

// JavaScript
window.alertFromDotNet = (msg) => {
    alert(msg);
};
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Deployment Strategies

Deploy to Azure Static Web Apps, GitHub Pages, or any static file host. Ensure dotnet publish -c Release -o ./publish is used.