LINQ - IEnumerable.Join on Anonymous Result Set in VB.NET
- by user337501
I've long since built a way around this, but it still keeps bugging me... it doesnt help that my grasp of dynamic LINQ queries is still shakey.
For the example:
Parent has fields (ParentKey, ParentField)
Child has fields (ChildKey, ParentKey, ChildField)
Pet has fields (PetKey, ChildKey, PetField)
Child has a foreign key reference to Parent on Child.ParentKey = Parent.ParentKey
Pet has a foreign key reference to Child on Pet.Childkey = Child.ChildKey
Simple enough eh?
Lets say I have LINQ like this...
Dim Q = FROM p in DataContext.Parent _
Join c In DataContext.Child On c.ParentKey = p.ParentKey
Consider this a "base query" on which I will perform other filtering actions.
Now I want to join the Pet table like this:
Q = Q.Join(DataContext.Pet, _
Function(a) a.c.ChildKey, _
Function(p As Pet) p.ChildKey, _
Function(a, p As Pet) p.ChildKey = a.c.ChildKey)
The above Join call doesnt work. I sort of understand why it doesnt work, but hopefully it'll show you how I tried to accomplish this task.
After all this was done I would have appended a Select to finish the job.
Any ideas on a better way to do this? I tried it with the PredicateBuilder with little success. I might not know how to use it right but it felt like it wasnt gonna handle the joining.
