When I define my class properties with out using fields (which was enabled with C# 3.0), class diagram is not showing my one to one/many relationships. Inheritance is visible in
This combines with Visual Studio and does everything you want to do with Class diagrams. http://modeling.codeplex.com/
It's for people like me who do not find where is the menu item in 1 minute.
In Visual Studio 2013: right click the class, click Add, and select the desired relationship.
More information: http://msdn.microsoft.com/en-us/library/ff657806.aspx
Since someone asked how to download files from old codeplex.com, I will briefly explain the steps below.
When you right click on the field or property you can select show as association or show as collection association.