it can be like,
<add key=".[your connection string key name you choose to have]." value="..[connection string value]..">
But it gives the following error:-
Error1: The tag 'appsetting' does not exist in XML namespace 'http://schemas.microsoft.com/winfx/2006/xaml/presentat
Error2:The type 'appsetting' was not found. Verify that you are not missing an assembly reference and that all referenced assemblies have been built.