我在Framework 3.5中创建了我的第一个项目，并且我转换为框架4.5并且它完美地工作。其次，我尝试将此项目的引用添加到在框架4.5中创建的另一个项目。在添加引用后构建我的第二个项目时，我收到一条错误消息：
1. The primary reference "xxx" could not be resolved because it was built against the ".NETFramework,Version=v4.5" framework. This is a higher version than the currently targeted framework ".NETFramework,Version=v3.5".
2. The type or namespace name 'xxx' could not be found (are you missing a using directive or an assembly reference?)
建议我遗漏的地方