To open DLL files
DLL stands for "Dynamic Link Library". DLL files are not integrated in a program, programs can, however, get DLL-files additional functionality and additional libraries. A DLL file can be used by multiple programs.
- To open a DLL file, you need a Decompiler, which reads the source code. You can open the file in a simple Editor, you get a result of only illegible characters.
- A popular and free Decompiler for .net applications is dotPeek.
- You have installed a Compiler, you can open the DLL file in it. It converts the content into a readable Code.

Free Decompiler dotPeek
How to make a DLL file install, learn, in a further practical tip.