I use the app.config file to store some values (Security key). These settings are used at runtime now i am making the exe of my project. but i will get an error showing security key doesn't found. I am adding app.config file in application folder is it correct? Can anybody help me please. Where i can get reference of app.config file when creating exe.

Thanks in advance.

By "application folder" do you mean the project folder or the build folder?
If you just add a single app.config file to your project then it is automatically copied to the build folder with the same name as the app but with an added .config extension (e.g. MyApp.exe.config).
It is also included as one of the files in a Primary output for ... in a setup project.