问题：第一次写C#,在命名空间中已经使用了using System.Configuration;但是使用Configuration时却无法使用;
解决方案：在解决方案资源管理器中，右击“引用”，“添加引用”，把“System.Configuration”添加进来就可以了;
问题2：为什么using System.Configuration;后还需要添加System.Configuration;
理解：When you add the reference you are asking the dll to be copied to the bin folder on compile/ build. Some dll's seen as core are added when the project is created, ie when you go file->new project so the references are set up at that point. They all have to go through the same process just that some are done for you and some you have to do manually. You could test it out by deleting the reference to your System dll and watching all your code fail.
(有时间再翻译给大家 : )