Mastering Source Generators in C#

Source Generators in C# are a compiler feature introduced in .NET 5. They inspect your program's syntax and semantics, then generate additional source files that are compiled together with your code.

Unlike traditional code generation, Source Generators do not modify existing code. They hook into the compilation process, analyze the codebase, and produce C# source files that the compiler then compiles into the final assembly.

Each generator implements the ISourceGenerator interface, which initializes with an Initialize method. This method registers callbacks that react to changes in the user's code, triggering code generation.

During the Execute method, a generator can access a Compilation object representing the user's code and use it to generate new syntax trees, which are added to the compilation.

Source Generators improve performance by moving code generation to compile time, reducing runtime overhead. They also provide immediate feedback in the IDE, catching potential issues earlier.

Generators can be used for AOP, creating boilerplate code, implementing the 'record' type functionality before C# 9, or auto-generating API clients from service definitions.

Source Generators are powerful but have limits. They cannot modify existing code and have no access to the project's semantic model post-compilation. Understanding their capabilities is crucial for effective use.