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With EF, if you navigate to a singular related entity within a select projection(such as from the many side of a many-to-one or 1-to-1/0) it would coalesce nulls and give you a left join: https://stackoverflow.com/a/2525950/84206

Since it occurs in a project and not in a join, EF makes a pretty reasonable assumption that a left join is desired. However, I haven't found a way to accomplish this in LINQ with LLBLGen. The above technique produces an inner join with LLBGen. I can't use techniques that use DefaultIfEmpty because that's only available when navigating into a many relationship.

I am hoping to avoid using WithPath/Prefetch because I'd really like to do the projection in LINQ instead of grabbing a huge object graph into memory and do the projection in memory.

This is LLBLGen 3.5.

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AaronLS
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If the FK is nullable, the join will be a left join. If the FK isn't nullable, it will be an inner join. This is the only way it's determinable what you want as Linq lacks any other system to specify the join type in this. Your link must use a nullable (optional) FK side as well to get a left join.

If nothing helps, please use queryspec, the query api will allow you to specify the join type in any case.

ps: please next time post on our forums, we don't monitor SO every day, but we do monitor our forums.

Frans Bouma
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  • In my case it was not working as expected because it is a 1-to-1/0 which is a **shared primary key relationship**. So the source PK/FK is non nullable, and probably triggered the "If the FK isn't nullable, it will be an inner join." even though it is an optional relationship based on the existence of the other entity. – AaronLS Aug 30 '13 at 19:27