Q:

Why is Visual Studio creating two DLLs with the same name in the bin folder?

For some of my Visual Studio solutions it is creating two DLL files in the bin folder which both appear to have exactly the same name, but when I look at their properties one is an 'Application extension (.dll)' and the other a 'CONFIG File (.config)'. 
Why do they both have the same name and why isn't the config one called 'ProjectName.config'?

A:

The file names created by VS are ProjectName.dll and ProjectName.dll.config.
If you are using Windows, it is most likely hiding common file extensions. This makes it appear that the files have the same name. To see the actual name:

Open the folder in Explorer
Navigate to View -> Folder Options -> Advanced
Clear the checkbox for the option "Hide extensions for known file types"

Now you should be able to see the full name of the file along with any extension. More details are available on the following page: Show or hide file name extensions.
For more information about .config files, see Configuration Files.

