Linq to object - Select Distinct

I can't quite figure out why this Linq Statement isn't working as i would expect:

    Dim distinctSurchargesList = (From thisparent As Parent In ThisParentCollection _
                                    From thisChild As Child In thisparent.theseChildren _
                                    Select New With 开发者_如何学运维{.childId = thischild.Id}).Distinct()

I would assume that this would create a new collection of anonymous types, that would be distinct. Instead it creates a collection the size of the "ThisParentCollection" with duplicate "MyAnonymousType" in it (duplicate id's).

Can anyone tell me where im going wrong?

Thanks

Your collection of anonymous types will be compared for equality by reference value - not by the value of the childId field. Each anonymous type will have a different object reference, hence they are all distinct.

Just select the ID, and don't project it into an anonymous type.