C#: how to programmatically create a class library DLL using reflection?

Suppose my code possesses the knowledge about the metadata of a nonexistent class library "mytest.dll", such as the types in this library, the functions of the types, the parameters and return types of the functions, etc.

How does my code manufacture this DLL using techniques such as reflection?

I know my code can generate the "mytest.cs" text file, then execute the compiler to produce the DLL, then delete the "mytest.cs" file. Just want to know if there are "more advanced" or "cooler" ways to do it.

Thanks.