.NET can do it:

https://learn.microsoft.com/en-us/dotnet/framework/reflectio...

See also - Source Generators, which can replace some forms of reflection.

https://learn.microsoft.com/en-us/dotnet/csharp/roslyn-sdk/s...

A big reason why this kind of stuff doesn't quickly become unreadable in C# is that the output of a source generator must be a new file. So the ability to extend existing code is limited to the facilities that the language specifically provides for this purpose (partial classes & members, extension methods etc). It also means that tooling can treat all such generated code as virtual files, allowing them to be inspected, debugged etc.

I meant this which is different: https://learn.microsoft.com/en-us/dotnet/fsharp/tutorials/ty...

For example, there is an SQL provider that gives you generated types and auto-complete but it does this without running a source generator that emits files. It just happens inside the compiler.