public List <Node> GetNodes(int courseId, int?parentId) { try { db.ClearCache(); Course course = db.Courses.SingleOrDefault(c => c.Id == courseId); List <Node> nodes = course.Nodes.OrderBy(n => n.Position).ToList(); if (parentId == null) { nodes = nodes.Where(n => n.ParentId == null).ToList(); } else { nodes = nodes.Where(n => n.ParentId == parentId).ToList(); } return(nodes); } catch (Exception) { return(new List <Node>()); } }