Please Recommend A Document Management System Plugin

I need to integrate a document management system in my asp.net app.   I need a code base to start with and did some googling but didn't find much.
Here are the requirements...
- Documents stored in SQL
- Nested Folders
- Sophisticated security levels (folder level security and item level)


Some optional things to have but not required...
- Treeview view of library structure
- Versioning 
- C# code base
- .NET 3.5




Thanks fellas.  I appreciate ANY and ALL suggestions.  :)
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