您不能使用SL5类库在ASP网站项目，因为他们有不同的运行时间。有时，它的工作原理，当库是简单的，但在你的情况下，图书馆有依赖System.Runtime.Serialization。

You can not use SL5 class library in asp web site project, because they have different runtime. Sometimes it works, when library is simple, but in your case library has dependency on System.Runtime.Serialization.

如果你需要共享SL和ASP项目之间的code，您可以创建简单的.NET类库（不SL5）和SL5库中添加所有文件的链接。NET库（添加/现有项目。 .. /加为链接）。添加引用新的库为你的asp网络项目，并删除旧的（SL5）库。

If you need share your code between SL and ASP projects, you can create simple .Net class library (not SL5) and add all you files from SL5 library as link to .Net library (Add/ Existing item... / Add as Link). Add reference to new library for your asp web project and remove old (SL5) library.

这是共享不同的库类型之间code的一种方式。也许你不能建立新的图书馆，如果你有SL具体依赖于你的code。我希望我的想法会帮助你。

It's one way to share code between different libraries types. Probably you can not build new library if you have SL specific dependency in your code. I hope my idea will help you.