bool isNew = false;
            FamiliesEntity ate = new FamiliesEntity(CTid);
            isNew = ate.IsNew;
            ate.UserId = UserId;
            ate.Name = name;
            ate.Description = txtDescription.Text.Trim();
            ate.CreateDateTime = DateTime.Now;
            ate.Save();

            if (isNew)
            {
                FamilyUsersEntity fuentity = new FamilyUsersEntity();
                fuentity.UserId = UserId;
                fuentity.FamilyId = ate.FamlyId;// foreign key
                fuentity.Save();
            }

Is my way right? but if i have many FamilyUsersEntity , how to save them? Thank you

            bool isNew = false;
            FamiliesEntity ate = new FamiliesEntity(CTid);
            isNew = ate.IsNew;
            ate.UserId = UserId;
            ate.Name = name;
            ate.Description = txtDescription.Text.Trim();
            ate.CreateDateTime = DateTime.Now;
            //ate.Save();

            if (isNew)
            {
                FamilyUsersEntity fuentity = new FamilyUsersEntity();
                fuentity.UserId = UserId;
                ate.FamilyUsers.Add(fuentity);
            }

            ate.Save(true);

great

Thank you