LINQ Select and insert: Am I trying to be too clever here? (updated)

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C#

.NET

LINQ

C#4.0

Hi
I am trying to use Linq-to-SQL to select some values from a db and insert a new record based on those values. In SQL I would write it like:

INSERT INTO RunPlatform(
platform_id,
build_env,
go_args,
--etc...
)SELECT
pp.platform_id,
pp.build_environment,
pp.go_args,
--etc...
FROM
DecoPlatforms dp
INNER JOIN ProductPlatforms pp ON dp.prodplat_id = pp.prodplat_id
WHERE dp.deco_id = 555

I tried writing this using linq extensions like so:

db.RunPlatforms.InsertAllOnSubmit
    (
        DecoPlatform.QueryByDecoId(Run.GetDecoIdFromRun(runId, db),db)
        .Join(
                ProductPlatform.Query(db),
                dp => dp.prodplat_id,
                pp => pp.prodplat_id,
                (dp, pp) => pp
            )
            .Where(pp => buildOnlyNotTestOnly == null || pp.build_environment == ((bool)buildOnlyNotTestOnly ? "T" : "F"))
            .Select(pp => new RunPlatform
            {
                platform_id = pp.platform_id,
                build_env = pp.build_environment,
                go_arg = pp.go_arg,
                bits = pp.bits,
                baseline_id = (int)pp.baseline_id,
                t3_osmap = pp.t3_osmap
            })
    );

Each [object].Query(db) simply checks if context (db) is null, creates a new db instance only if it is null, and returns the db.[object]s as an IQueriable<[object]>. Any [object].Query...() may perform some actions to narrow the IQueryable<[object]> set but each checks the db for null and always passes it's own instance down the line finally to [object].Query(db). I have included the DecoPlatform class below as an example of this.

[DecoPlatform class]

partial class DecoPlatform
    {
        public static IQueryable Query
            (
                CarmaContext db = null
            )
        {
            if (db == null)
                db = new CarmaContext();
            return db.DecoPlatforms;
        }

        public static IQueryable QueryByDecoId
            (
                int decoId,
                CarmaContext db = null
            )
        {
            if (db == null)
                db = new CarmaContext();
            return Query(db).Where(dp => dp.deco_id == decoId);
        }

    }

But I get the error 'Explicit construction of entity type 'SQLDataAccess.CarmaEntityFramework.RunPlatform' in query is not allowed.'.

Question: How do I manage to get the IEnumerable<runplatform> list from the linq?

For now I have two phases; First a IEnumerable<productplatform> select and then the context insert all with the new RunPlatform class'.

I could use this solution but I hoped the problem was simple / easy enough to investigate. I mean, I gotta learn sometime, right? ^_^

Thanks in advance
G