NClass

First thing I've come across that will allow you to upload a DLL of a C# solution and build a UML Class Diagram from it, complete with relationships, and has the ability to export back out to PDF. Powerful for a free tool. Some minor critiques: 1) It doesn't have any integration with Visual Studio to allow you to drag-and-drop classes and then create the relationships between them, you'd have to build them from scratch or import everything from the DLL - we were trying to replace the existing Visual Studio plug-in with something more robust that would allow us to select individual classes upfront. (We could delete the classes after-the-fact). 2) When it draws the relationship lines between the classes, it does it by overlapping the lines over top of the boxes that have your classes, instead of placing the lines behind or to the side of them. It does allow you to drag the boxes around, which is ok, but not great, since it'd be nicer not to have to, to begin with. (Much better than no editing at all, though!) 3) The use isn't obvious on how to get operations to not be greyed out - like I had to guess that creating a "project" within the application would allow "Import Assembly" to be ungreyed out once I gave my project a name within the application. It will work to do the job it was created to do, and even fills a niche I haven't seen a lot of these so-called UML products filling (most seem to be just online versions of Visio with no ability to reverse-engineer a diagram from code whatsoever), but it's very basic - especially in the styling and additional diagrams availability, of which it can only do a Class Diagram and maybe a flowchart if you did it manually - and you'll have to correct the relationship lines yourself.

Thank you so much for the simple yet very powerful tool! Nice usability, nice design!

I was looking for a class diagram tool with code generation for C#. Just needed to diagram simple classes, and this program fills the bill. It is simple to use, and the code generated is just what I was looking for.

This is the best class diagram creator for me. It has a simple interface and fully customizable. Thanks a lot!

Excellent @ All.