Source Generators are the "Modern Reflection." They allow you to write code that runs During Compilation and generates MORE code for your project.
Reflection takes time at startup. Source Generators do the work once at compile time. Example: Instead of using Reflection to find all JSON properties, a Source Generator writes the serialization code directly into your partial class. This leads to **Instant Startup** and zero runtime overhead.
Native AOT (Ahead of Time) hates reflection. Source Generators are the solution. By moving all "Dynamic" logic to the compilation phase, you can build extremely fast, small, and secure binaries that are perfect for the cloud.
Q: "Can a Source Generator modify existing code?"
Architect Answer: "NO. Source Generators can only **ADD** new code to your project. They cannot delete or change existing lines. This is by design, as it ensures that the original source code remains predictable and easy to debug. To 'modify' behavior, we usually use **Partial Classes** or **Partial Methods** so the generator can provide the implementation for a method you defined."