EntityFramework Linq 获得所有数据，包括子节点

public static class EntitiesContextExtensions
{
    /// <summary>
    /// 获得用户拥有的角色
    /// </summary>
    /// <param name="entities"></param>
    /// <param name="userID">
    public static List<string> GetUserAllPositionIDs(this YESWEB.DB.Business.EntitiesContext _entities, string userID)
    {
        //获得用户所属的职位,包含子职位
        var query = _entities.base_position.Where(w => _entities.base_userRelation.Any(u => u.Category == 1 && u.UserID == userID && u.ObjectID == w.RowID)
        ).ToList();
        //if (query.Count == 0) return new List<string>();
        var _IuserRelation = query.Concat(query.SelectMany(t => getAllChildren(_entities.base_position, new String[] { t.RowID }, obj => obj.RowID, obj => obj.ParentID)));

        var userAllpositionID = _IuserRelation.Select(p => p.RowID).Distinct().ToList();

        if ((userAllpositionID.Count == 0) || (_entities.base_position.Any(w => (userAllpositionID.Contains(w.RowID)) && (w.IsAlone != "Y"))))
        {
            string everyID = _entities.base_position.Where(w => w.PosCode.ToLower() == "everyone").Select(s => s.RowID).FirstOrDefault();
            userAllpositionID.Add(everyID);
        }

        return userAllpositionID;
    }

    private static IEnumerable<T> getAllChildren<T>(IEnumerable<T> Data, IEnumerable<string> rowIDs, Func<T, string> funcID, Func<T, string> funcParentID)
    {
        var query = (from c in Data
                     where rowIDs.Contains(funcParentID(c))
                     select c).ToList();
        return query.Concat(query.SelectMany(t => getAllChildren(Data, new String[] { funcID(t) }, funcID, funcParentID)));
    }
}