I have found a problem when doing an outer join after a nested query. The following is a stripped down way to reproduce it (Northwind):

from ep in db.Employees.Where(f => f.Country == "UK")
                    join et in db.EmployeeTerritories on ep.EmployeeID equals et.EmployeeID into etg
                    from et in etg.DefaultIfEmpty()
                    select ep

This throws

An exception was caught during the execution of a retrieval query: The multi-part identifier "LPLA_2.EmployeeID" could not be bound..

With the following SQL

exec sp_executesql N'
SELECT  [LPA_L1].[EmployeeID], [LPA_L1].[LastName], [LPA_L1].[FirstName], [LPA_L1].[Title], 
        [LPA_L1].[TitleOfCourtesy], [LPA_L1].[BirthDate], [LPA_L1].[HireDate], [LPA_L1].[Address], [LPA_L1].[City], [LPA_L1].[Region], 
        [LPA_L1].[PostalCode], [LPA_L1].[Country], [LPA_L1].[HomePhone], [LPA_L1].[Extension], [LPA_L1].[Photo], [LPA_L1].[Notes], 
        [LPA_L1].[ReportsTo], [LPA_L1].[PhotoPath] 
FROM 
( 
    (
        SELECT  [LPLA_1].[EmployeeID], [LPLA_1].[LastName], [LPLA_1].[FirstName], 
                [LPLA_1].[Title], [LPLA_1].[TitleOfCourtesy], [LPLA_1].[BirthDate], [LPLA_1].[HireDate], [LPLA_1].[Address], [LPLA_1].[City], 
                [LPLA_1].[Region], [LPLA_1].[PostalCode], [LPLA_1].[Country], [LPLA_1].[HomePhone], [LPLA_1].[Extension], [LPLA_1].[Photo], 
                [LPLA_1].[Notes], [LPLA_1].[ReportsTo], [LPLA_1].[PhotoPath] 
        FROM    [Northwind].[dbo].[Employees] [LPLA_1]  
        WHERE 
        (
            (
                [LPLA_1].[Country] = @Country1
            )
        )
    ) [LPA_L1]  
    LEFT JOIN   [Northwind].[dbo].[EmployeeTerritories] [LPA_L2]  
        ON      [LPLA_2].[EmployeeID] = [LPA_L2].[EmployeeID]
)
',N'@Country1 nvarchar(15)',@Country1=N'UK'

Interestingly, it works if you use an inner join, likewise if you dont do the nested .Where() it runs fine.

Dont you just love Aliases!

Thanks again!

Alias is my middle name How many times an issue is about a wrong alias... I stopped counting. And I payed a lot of attention to the alias system to get it right. Will check it out.

Fixed it It was a very obscure bug, where aliases of a groupjoin had to be rewritten, and as a clone was used, it didn't clone a part of the tree, so it was changing the wrong object

(edit) for a temporary build, see this post: http://www.llblgen.com/tinyforum/GotoMessage.aspx?MessageID=74230&ThreadID=13312 (does require latest temporary runtime lib build, available in this post: http://www.llblgen.com/tinyforum/GotoMessage.aspx?MessageID=74164&ThreadID=13312