Last analysis failed Analysis ID "e381e04d-83dc-41eb-b6f8-1c5d0f412f3d"

I am getting an error I have deleted the project and recreated it and it is still happening

Hi, it appears the project does not compile:

CS0234 The type or namespace name 'Forms' does not exist in the namespace 'System.Windows' (are you missing an assembly reference?)