Detect unknown shadow primary key values when attempting to save owned collection #25652
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…d collection Fixes #19856 The fundamental issue here is that the key for owned collections is, by default, formed from shadow properties. This means the values of these properties are lost when the entities in the collection are no longer tracked by a DbContext. When the entities are then later attached there is no way to get these values back. (Contrast this with owned non-collection entities, where the shadow key value can be synthesized from the owner key.) This in turn means that there is no way to identify these entities in the database, and there is therefore no way to update or delete them. This PR detects this situation and throws an exception with a (hopefully) helpful error message. The best way to deal with this is to add a CLR property for the key (which can be private) to the owned entity type. The key values are then preserved while the entities are not being tracked, and re-attaching the entities works correctly. We should document this.
Also, fixes #21206. Let value generators indicate that they return stable values, and don't mark these values as Unknown. This stops values generated for discriminator properties from being marked as Unknown.
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AndriySvyryd
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Aug 23, 2021
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Fixes #19856
The fundamental issue here is that the key for owned collections is, by default, formed from shadow properties. This means the values of these properties are lost when the entities in the collection are no longer tracked by a DbContext. When the entities are then later attached there is no way to get these values back. (Contrast this with owned non-collection entities, where the shadow key value can be synthesized from the owner key.) This in turn means that there is no way to identify these entities in the database, and there is therefore no way to update or delete them.
This PR detects this situation and throws an exception with a (hopefully) helpful error message.
The best way to deal with this is to add a CLR property for the key (which can be private) to the owned entity type. The key values are then preserved while the entities are not being tracked, and re-attaching the entities works correctly. We should document this.
Fixes #21206.
Let value generators indicate that they return stable values, and don't mark these values as unknown. This stops values generated for discriminator properties from being marked as unknown. Also, use the correct derived entity type when generating a discriminator value.