Blazor is a framework for creating interactive web applications with C# and .NET, developed by Microsoft. It uses a component-based development model, similar to React or Angular, but allows developers to write code for both client-side and server-side logic in C#.
Blazor can operate in two main modes:
In Blazor Server, the application runs on the server. Only page rendering and updating of the DOM (Document Object Model) takes place on the client via a SignalR connection.
<aside> ℹ️ SignalR is a library for ASP.NET that facilitates real-time communication functionality in web applications. Using SignalR, features such as dynamic content updates, push notifications, and real-time chat can be added, all without having to reload the web page. SignalR uses different transports to ensure communication between client and server, depending on the capability of the browser and server including WebSockets which is the preferred transport method for two-way communication, Server-Sent Events and Long Polling.
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In Blazor WebAssembly, the application runs entirely in the client's browser using WebAssembly.
In a Blazor WebAssembly (WASM) application, Dynamic Link Libraries (DLLs) are used to include the libraries and dependencies needed for the application. This is a key aspect that allows .NET code to be executed within a browser. Here is how the mechanism of DLLs works in a Blazor WebAssembly App:
When you compile a Blazor WebAssembly App, the C# code and dependencies for the project are compiled into DLLs, just as they are for traditional .NET applications. This includes the DLLs for the application itself, as well as those for all the libraries and frameworks used (such as .NET Standard, .NET Core, and third-party libraries).
During the build process, all necessary DLLs are minified and optimized for download by the client.
The resulting DLLs are included in the application's deployment package and are served by the Web server when a client accesses the application. These DLLs are placed in a folder called _framework within the published application structure.
When a user accesses a Blazor WebAssembly App, the browser downloads the initial HTML, the bootstrap JavaScript file (blazor.webassembly.js), and all the necessary DLLs.
The bootstrap JavaScript file handles the initialization of the WebAssembly environment in the browser.
<aside> ℹ️ Blazor WebAssembly includes a stripped-down version of the .NET runtime (the mono runtime, adapted for WebAssembly), which is downloaded along with the application and is responsible for loading and executing the downloaded DLLs in the browser context.
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The blazor.boot.json file is a configuration file used to manage the resource information needed to start the Blazor WebAssembly application. It contains crucial metadata such as the list of assembly (.dll files) needed, their hashes, sizes, and URLs of where to find them in the server filesystem. During the initial loading of the application, the browser reads this file to determine which resources to download and store in the browser's local cache.