CODEWITHSUNDEEP
linqentity-frameworkt-sqlentity-framework-4linq-to-entities
slippyr4
slippyr4

Reputation: 862

EF query to select available association entities

I am sure I could google this if I knew what to search for, if that makes sense. I'm trying to get the hang of entity framwork, and considering how i would implement some real-world scenarios in it.

Imagine a simple data model with a Person entity, and a Color entity, and an association called ColorsLiked.

I want to use Color a bit like an enum; there will only be 3 defined (red, green, blue).

I want a drop-down to allow the used to add Colors to their list of colors they like - which is all easy enough. But, what query can I use to select only the colors the person doesn't already like? i.e so that as they pick a color, it is no longer available for selection in the list.

In SQL, it's a simple query with a left outer join. But I don't understand how to do something like this in EF.

any guidance would be appreciated

slip

Upvotes: 0

Views: 88

Answers (1)

JamesF
JamesF

Reputation: 402

Assuming that you want all the colors the person has not yet liked this is the LINQ expression to do that. 

var unlikedColors = allColors.Except(person.ColorsLiked);

Upvotes: 1

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