I came across this problem today when migrating a project from VS 2008/.NET 3.5 to VS 2010 RC1/.NET 4.0. I don’t actually think it’s a VS 2010 thing, though.
I have two entities A and B. There is a navigation property on A, and it can have either one or no instances of B. B’s foreign key is to A’s primary key (obviously) but B also has its own primary key.
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