Hosting Models of Blazor Application

Blazor offers two primary hosting models for building interactive web applications: Blazor WebAssembly (Client-Side) and Blazor Server (Server-Side). Both models allow you to build rich, modern web UIs using C# instead of JavaScript, but they have different approaches to running and rendering applications.

Here’s an overview of each:

1. Blazor WebAssembly (Client-Side)

In the Blazor WebAssembly model, the app runs entirely on the client’s browser using WebAssembly. When the application is loaded, the necessary code (including the .NET runtime) is downloaded to the browser, and it runs in a secure sandboxed environment. This makes the app independent of the server after the initial load.

• How it works:

  • The browser downloads the Blazor app, the .NET runtime, and the application assemblies.
  • The app runs entirely on the client-side inside the browser.
  • WebAssembly is used to execute .NET code in the browser.

• Benefits:

  • Offline support: Once loaded, the app can continue to work offline.
  • Full client-side processing: No need for server round trips for every user interaction.
  • Cross-platform: Works on any modern web browser (Chrome, Firefox, Edge, Safari).

• Drawbacks:

  • Large initial download size: The application must download the .NET runtime and app files, which could slow down initial load times.
  • Limited access to server resources: You still need to use HTTP requests (e.g., REST APIs) for server interaction.

• Use cases:

  • Progressive Web Applications (PWAs): Apps that need to work offline or behave like native apps.
  • Apps with low-latency requirements: Since all processing happens client-side, user interactions are instant.

Example:

Blazor WebAssembly: https://yourapp.com/_framework/blazor.webassembly.js

• A PWA such as a task management app that needs offline support.
• Client-side rendering: E-commerce sites where all interactions like product filtering, sorting, and selection are done in the browser.

2. Blazor Server (Server-Side)

In the Blazor Server model, the application runs on the server, and the UI updates are sent to the client in real-time via SignalR (a WebSockets-based protocol for real-time communication). Only minimal data (events and UI updates) is transmitted between the client and server, while all logic is executed on the server.

• How it works:

  • The app runs on the server.
  • The client communicates with the server through a SignalR connection.
  • UI updates and events (such as clicks) are passed between the client and server in real-time.

• Benefits:

  • Minimal download size: No need to download the entire .NET runtime or app code to the client.
  • Supports thin clients: Since processing happens on the server, it works well on devices with limited resources.
  • Centralized app logic: Business logic stays on the server, reducing the risk of exposing sensitive logic to the client.

• Drawbacks:

  • Requires an active server connection: The app is unusable without connectivity to the server.
  • Latency issues: Round-trip communication between the client and server can cause delays, especially in high-latency networks.
  • Server scalability: Since the server handles all the processing, it needs more resources as the user count increases.

• Use cases:

  • Line-of-business (LOB) apps: Internal business apps with complex data interactions but relatively few users.
  • Admin dashboards: Applications where real-time updates are required and maintaining control over the data is critical.

Example:

Blazor Server: https://yourapp.com/_framework/blazor.server.js

• Admin panel for managing data, where real-time communication between the client and server is essential.
• Customer support chat applications where server-side processing ensures secure data handling.

3. Hybrid Hosting Model (Blazor Hybrid)

Although not a typical hosting model for web applications, Blazor Hybrid is worth mentioning. It allows you to run Blazor applications in a native .NET MAUI (Multi-platform App UI) or Electron desktop app. In this model, the Blazor components run inside a native shell, offering the benefits of native access while still using Blazor for UI.

• Benefits:
  • Full access to native APIs (e.g., camera, Bluetooth, etc.).
  • Runs outside the browser, allowing desktop-style applications with web technologies.
• Drawbacks:
  • Requires packaging as a native application, so it’s less suited for traditional web use cases.

Example:

• A desktop application for accounting software that runs in Electron using Blazor components for UI but native features for system interaction.

Comparison Table: Blazor WebAssembly vs Blazor Server

Summary of Hosting Models

1. Blazor WebAssembly: Best for applications where you want to run the app entirely in the browser, especially for offline-first experiences.
   • Example: A Progressive Web App like a task manager or productivity tool.
2. Blazor Server: Ideal for applications where you need real-time data interaction or need to control logic on the server.
   • Example: A line-of-business (LOB) app or a dashboard where real-time updates are critical.

Blazor’s flexibility allows developers to choose the right hosting model based on the requirements of the application, whether it’s an interactive client-side app with offline support or a server-centric app with real-time UI updates.