SystemReflectionEmit

System.Reflection.Emit is a namespace within the .NET Framework that provides a way to dynamically generate and emit Microsoft intermediate language (MSIL) code at runtime. This allows developers to create assemblies and types on the fly, rather than having them pre-compiled. The primary classes within this namespace are `AssemblyBuilder`, `ModuleBuilder`, and `TypeBuilder`, which facilitate the construction of new assemblies, modules, and types respectively.

Developers can use `System.Reflection.Emit` to generate code for various purposes. This includes scenarios where the code to be executed is not known until runtime, such as in Just-In-Time (JIT) compilation, dynamic proxies, or domain-specific languages. The emitted MSIL can then be loaded and executed by the .NET runtime.

The process typically involves defining a new assembly, adding modules to it, and then defining types within those modules. For each type, methods, properties, and fields can be defined. The body of these methods is constructed by emitting MSIL instructions. While powerful, `System.Reflection.Emit` is a low-level API, requiring a deep understanding of MSIL and the Common Language Runtime (CLR). Consequently, it is often used in more advanced scenarios or by libraries that abstract away its complexity.