参考地址:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpgenref/html/cpconBaseClassUsageGuidelines.asp
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpgenref/html/cpconBaseClassUsageGuidelines.asp
“尽可能地使用基类, 而不是interface”
