‘System.Configuration.ConfigurationSettings.AppSettings’ is obsolete: ‘This method is obsolete, it has been replaced by ConfigurationManager.AppSettings’
It’s just a warning. Your application will still build and work. If you want to fix this warning, just add a reference in your project to the System.Configuration.dll (Add Reference > System.Configuration) and use the ConfigurationManager class instead of ConfigurationSettings. Now the warning won’t show up any more.
If you use the ConfigurationManager class and do not add the reference to the System.Configuration.dll, than the compiler will give an error saying that ‘ConfigurationManager’ does not exist.