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Imported function in Entity Framework Where clause?

Answer 1

A:

I don't think you want to pass this expression as a string. You want a proper lambda expression like:

MyContext.MyEntities.Where( entity => MyContext.MyFunction(entity.ID ) );

jlew 2009-06-29 16:44:52

Thanks Jeremy - however, as the function isn't returning an entity (just a Boolean) it doesn't exist in the class of MyContext (although I can successfully call it via and EntityClient).

Lee Atkinson 2009-06-29 16:53:09

Well, where does it exist? Just call it on the right hand side of the => just like you would from anywhere else.

jlew 2009-06-29 17:17:05

It doesn't exist as a member of the DataContext object as generated by the Entity framework) as it's not a entity-returning function - it's a boolean-returning.

Lee Atkinson 2009-06-29 19:20:42

Take a look at the documentation of the Where extension method[1]. The Where method accepts a function (delegate) which accepts a typed Entity and returns a boolean. The lambda expression which I supplied (modified to be syntactically correct, since you pointed out that it exists somewhere other than MyContext), will work just fine as a filter for the Where method, and the result will be a collection of entities which "pass" the filter.[1] http://msdn.microsoft.com/en-us/library/system.linq.queryable.where.aspx

jlew 2009-07-01 17:15:52

But that will result in the where clause being evaluated on the client, won't it?

Lee Atkinson 2009-07-07 09:12:46

My bad, I didn't fully understand your question until now. Alex is absolutely right.

jlew 2009-07-07 15:07:21

Answer 2

+1 A:

The query you are trying to write is composing a call to a FunctionImport with a query over an EntitySet.

But because FunctionImports are wrappers around StoredProcedures, which are non-composable, this just won't work.

In order for something like this to work, theoretically the function would need to be a wrapper around something composable like a TVF (Table Value Function). But unfortunately TVFs aren't supported in the Entity Framework today.

Alex

Alex James 2009-06-29 22:04:01

Lee Atkinson 2009-06-30 08:38:34

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Imported function in Entity Framework Where clause?

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