How to open .dll files to see what is written inside?

you are better off with a decompiler like redgates .net reflector or jetbrains resharper decompiler. there are open source ones also like

http://www.jetbrains.com/decompiler/

http://ilspy.net/

Follow below steps..

1. Go to Start Menu.
2. Type Visual Studio Tool.
3. Go to the folder above.
4. Click on "Developer Command Prompt for VS 2013" in the case of VS 2013 or just "Visual Studio Command Prompt " in case of VS 2010.
5. After command prompt loaded to screen type ILDASM.EXE press ENTER.
6. ILDASM window will open.Drag the .dll file to window from your folder.Or click on File->New.Then Add required .dll file.
7. After above steps Mainfest and .dll file will appear. Double click on these files to see what it contains.

I think you have downloaded the .NET Reflector & this FileGenerator plugin http://filegenreflector.codeplex.com/ , If you do,

1. Open up the Reflector.exe,

2. Go to View and click Add-Ins,

3. In the Add-Ins window click Add...,

4. Then find the dll you have downloaded

5. FileGenerator.dll (witch came wth the FileGenerator plugin),

6. Then close the Add-Ins window.

7. Go to File and click Open and choose the dll that you want to decompile,

8. After you have opend it, it will appear in the tree view,

9. Go to Tools and click Generate Files(Crtl+Shift+G),

10. select the output directory and select appropriate settings as your wish, Click generate files.

OR

use http://ilspy.net/