Error: The name 'ConfigurationManager' does not exist in the current context

You need to reference System.Configuration.dll in your project as well as the "using" statement.

Namespaces are (sometimes) "split" across assemblies. That means that types in a single namespace are actually in different assemblies.

To determine which assembly a BCL or FCL type is in, look it up on MSDN. If you look at the help for ConfigurationManager, you'll see that it specifies that it's in the System.Configuration assembly by looking near the top at "Assembly". This is the assembly you need to reference from your project

I faced the same problem too.

I have 2 projects 1 main and 1 DLL. I have App.config file in the same Place But Connection string was defined in DLL but not in main project which is executable one as main. after adding / moving the connection string to main project APP.CONFIG file, the issue resolved.

Hope this helps

• at the solution explorer
• select References
• then click Add Reference from the right mouse button menu

• in the top right corner write "Configuration:
• check the System.Configuration, which would show up
• press OK

Philip was correct adding the reference helped me, but I actually went and tried to download the DLL because I did not know there was an easier way...

1. right-click on 'add references' folder in the solution explorer
2. select the '.NET' tab
3. search for the .NET reference you would like to add (in this case System.Configuration)

This post was very helpful to me, thanks to all.