Database is lock

ServiceStack.OrmLite
1

I got database is lock when run below code, could you tell me how to resolve it.
I want to create an new user. I refer my user table with UserAuth. So i must add user first and get it’s id, but i also want to add them in a transaction.

 public object Post(CreateUser request)
        {
            UserResponse userResponse;
                        using (var dbTrans = Db.OpenTransaction())
            {
                var user = new User();
                user.ClassId = request.ClassId;
                user.KindergartenId = request.KindergartenId;
                user.RoleType = request.RoleType;
                user.RealName = request.DisplayName;
                user.LoginName = request.UserName;
               
                Db.Save(user);

                var authRepo = this.TryResolve<IUserAuthRepository>();

                var newUserAuth = new UserAuth();
                newUserAuth.DisplayName = request.DisplayName;
                newUserAuth.UserName = request.UserName;
                newUserAuth.PhoneNumber = request.PhoneNumber;

newUserAuth.RefId = user.Id;

                //Create New GetUsers Account with oldUser Password
                var iUserAuth = authRepo.CreateUserAuth(newUserAuth, request.Password);

                newUserAuth.Id = iUserAuth.Id;
                if (request.RoleType == 1)
                {
                    authRepo.AssignRoles(iUserAuth, new List<string>() { "Parent" });
                }
                else if (request.RoleType == 2)
                {
                    authRepo.AssignRoles(iUserAuth, new List<string>() { "Teacher" });
                }
                else if (request.RoleType == 3)
                {
                    authRepo.AssignRoles(iUserAuth, new List<string>() { "Master" });
                }

                {
                    var ret = Db.Single<UV_UserAuthAndUser>(u => u.Id == iUserAuth.Id);
                    userResponse = new UserResponse().PopulateWith(ret);
                }
                                dbTrans.Commit();
            }

            return userResponse;
        }