I installed arcgis 10.5 trial and arcobjects 10.5 sdk .net from the web site. I have MVS 2015 community. But when I create a new project and try to add a class (lets say toolbar for arcmap), I get such an error "a file with the name 'blabla.cs' already exist or is open in an editor. Please give a unique name to the item you are adding, or delete the exisiting item first.". What should I do in order not to get such an error??