ctx.As.Select(a => new Thing
    {
        AId = a.Id,
        BNames = a.Bs.Select(x=>x.Name) //SubCollection
    })

[a].[Id] AS [AId] FROM [As] AS [a]

p_executesql N'SELECT [x].[Name]
FROM [Bs] AS [x]
WHERE @_outer_Id = [x].[AId]',N'@_outer_Id int',@_outer_Id=1

p_executesql N'SELECT [x].[Name]
FROM [Bs] AS [x]
WHERE @_outer_Id = [x].[AId]',N'@_outer_Id int',@_outer_Id=2