EF 4.0 LINQ one to many / many to one

Just starting to use LINQ as well as EF.

I have a set of tables in t开发者_开发技巧he following configuration:

PublicUtility (UtilityCode) * ----> 1 (UtilityCode) Utility (UtilityCode) 1 -----> * (UtilityCode) UtilityDetail

I have a query in SQL. Based on some other business rules this query will either return 1 value or NULL.

SELECT

@UtilityCode = UtilityDetail.UtilityCode

FROM

UtilityDetail

INNER JOIN PublicUtility ON

PublicUtility.SubdivisionCode = @SubdivisionCode AND

PublicUtility.Year = @PublicUtilityYear AND

PublicUtility.UtilityCode = UtilityDetail.UtilityCode

WHERE

UtilityDetail.DebtPurposeCode = @DebtPurposeCode

How could I rewrite this using LINQ to entities?

using (YourObjectContext ctx = new YourObjectContext())
{
    var code = (from ud in ctx.UtilityDetails
                join pu in PublicUtility on ud.UtilityCode equals pu.UtilityCode
                where ud.DeptPurposeCode == [code_value] && pu.SubdivisionCode == [subdivcode_value] && pu.Year == [year_value]
                select new {ud.UtilityCode}).FirstOrDefault();
}