Here is what I am trying:

[HierarchyRoot, Serializable]
    [TableMapping("CalendarEvents")]
    public class CalendarEvent : Entity
    {
        [Field, Key]
        public int ID { get; private set; }

        [Field]
        public int Year { get; private set; }

        [Field]
        public int Month { get; private set; }

        [Field(Nullable = false)]
        [FieldMapping("Year")]
        //[FieldMapping("Month")]
        public CalendarMonth CalendarMonth { get; set; }
    }

    [HierarchyRoot, Serializable]
    [TableMapping("CalendarMonth")]
    [KeyGenerator(KeyGeneratorKind.None)]
    public class CalendarMonth : Entity
    {
        [Field, Key(0)]
        public int Year { get; private set; }

        [Field, Key(1)]
        public int Month { get; private set; }

        [Field]
        public string UrlName { get; set; }
    }

Calendar and CalendarEvent are connected by the FK (Year, Month). How can I map this?

tobi

Updated at 11.08.2010 13:43:07

(Sorry for not answering for quite some time). I wanted to try this solution but I could not figure out how to map the CalendarMonth property to two db columns. I tried:

[Field(Nullable = false)]
        [FieldMapping("Year,Month")]
        public CalendarMonth CalendarMonth { get; set; }

and

[Field(Nullable = false)]
        [FieldMapping("Year")]
        [FieldMapping("Month")]
        public CalendarMonth CalendarMonth { get; set; }

but both did not work. Can you help out on how to map CalendarMonth to (Year, Month)?

Updated at 15.08.2010 10:33:17

Thank you for your very helpful offer! Here is my situation: I have decided to leave the sinking ship L2S and look for some other ORM. I like DO.NET very much because it became apparent to me by reading the manual that you guys really know what you are doing. So whenever I have time I do some testing with DO.NET to see if there are issues preventing a successful migration before I actually start the big work of migrating.

So far I have found only two issues: 1) I cannot map my existing database (and I always do database first because performance really matters for me and automatic upgrades are infeasible because of the data volume); 2) no join prefetching (yet).

1) I would thankfully take your offer of implementing the mapping of multi-column FKs because I would not want to change the DB schema as I then would also have to modify my existing ORM. 2) I have tried to made the case for this by email and will be sending additional info in a minute (I did some benchmarks today).

I would also point out that the query translator is really capable as I could execute some crazy queries ;-) Performance of compiled queries is also extremely good (350us for a 3 columns fetched by PK). All in all a superior product. What do you think about the two issues I posted above?

Updated at 18.08.2010 15:54:32

Very helpful, thank you. Please note that the first issue is a blocker for me that prevents me from pulling DO into production. I can live without the join fetch for a few month as I probably will implement that myself meanwhile in a hacky fashion on top of IQueryable.

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