How can I use external expressions in Linq with EF4 (and LINQKit)?
- by neo
I want to separate out often used expressions in linq queries. I'm using Entity Framework 4 and also LINQKit but I still don't know how I should do it the right way. Let me give you an example:
Article article = dataContainer.Articles.FirstOrDefault(a => a.Id == id);
IEnumerable<Comment> comments =
(from c in container.Comments
where CommentExpressions.IsApproved.Invoke(c)
select c);
public static class CommentExpressions
{
public static Expression<Func<Module, bool>> IsApproved
{
get
{
return m => m.IsApproved;
}
}
}
Of course the IsApproved expression would be something much more complicated.
The problem is that the Invoke() won't work because I didn't call .asExpandable() from LINQKit on container.Comments but I can't call it because it's just an ICollection instead of an ObjectSet.
So my question is: Do I always have to go through the data context when I want to include external expressions or can I somehow use it on the object I fetched (Article)?
Any ideas or best practices?
Thanks very much!
neo
