Entity-framework – Entity framework – “Problem in mapping fragments”-error. Help me understand the explanations of this error

entity-framework

Error 3007: Problem in Mapping Fragments starting at lines 186, 205: Non-Primary-Key column(s) [WheelID] are being mapped in both fragments to different conceptual side properties – data inconsistency is possible because the corresponding conceptual side properties can be independently modified.

I found several places on the web describing this error, but I simply don't understand them. (confused smiley goes here)

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There is something pretty fundamental here, I must be missing. Can you explain it, so that I understand it? Maybe using my real life example below?

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Foreign key 1:N Wheels.Id -> Slices.WheelId

I add them to entity framework, and WheelId is not visible in the Slices-entity.

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Doing some workaround (deleting the relationship from the db before adding tables to EF – then re-creating it and updating EF) I managed to get the WheelId to stay in Slices, but then I get the error mentioned at the top.

Best Solution

Since Slices.WheelId is an FK, you cannot expose it in your client model, period. There are ways to get the value, though.

var wheelId = someSlice.Wheels.ID;

Update In EF 4 you can do this by using FK Associations instead of independent associations.