I can't find the ConfigurationManager.

The first time you write C #, the using System.Configuration is already used in the namespace, but it is not available with the Configuration, and the workaround is: In Solution Explorer, right-click on "References", "Add References" and " System.Configuration "to add in.

Question: why the using System.Configuration; and then add system.configuration;

Understanding: When you add the reference, the asking the DLL to is copied to the Bin folder on Compile/build. Some dll ' s seen as core is added when the project is created, ie if you go file->new project so the references is S Et up at the point. They all has to go through the same process just that some is done for both and some you have to do manually. You could test it out by deleting the reference to your System DLLs and watching all your code fail.

(There is time to translate to everyone:)

I can't find the ConfigurationManager.