I created a SharePoint 2013 farm solution project in Visual Studio 2013 (running on the same machine where SharePoint 2013 server is running) with
event receiver. I added web.config at project root level to store connection string (I'm working off external SQL DB) and got the following error during deployement:
Error 27
Error occurred in deployment step 'Activate Features': Operation is not valid due to the current state of the object.
When I commented out the ConfigurationManager.ConnectionStrings["MyConnectionString"].ConnectionString; the error went away. Am I missing something or not supposed to add my own App.config to SharePoint project solution?