Hey
I don't know, if this is a bug, or a don't known issue...
Following steps to reproduce:
In mySQL create a Table with 3 Fields.
Let's say:
ID (BigInt) dID(BigInt) cID(Bigint)
All three fields have to be Primary
Then create a second table with one field
dID (BigInt)
OK - Now create a froeign key between dID SecondTable and dID First table
When yout then generate the model in the entity Designer (1.0.53) then you will see, that the designer will NOT create the association. (Maybe, he knows, that it won't work...)
Then add an association by hand, like above. - And Validate. It tells, everything is OK.
But when running a Linq with this fields, there will be an error.
So, please take a look on this behaivor