ASP.NET MVC-用户未处理的异常

如何解决ASP.NET MVC-用户未处理的异常

我的注册表格有错误，每当我按“提交”按钮时，都会显示错误并指出此错误：

System.ArgumentNullException：'字符串引用未设置为String的实例。参数名称：s

据我了解，我需要定义S参数。但是我一直出错，所以有人能启发我如何解决这个问题吗？

    [HttpPost]
    public ActionResult RegisterCustomer(UserRegister userRegister)
    {
        try
        {
            PBKDF2Hash PwdHash = new PBKDF2Hash(userRegister.Password);

            userRegister.Password = PwdHash.HashedPassword;

            sqlConnection conn = new sqlConnection(ConfigurationManager.ConnectionStrings["connSkoolaNewDB"].ConnectionString);
            sqlCommand cmd0 = new sqlCommand("select * from users where Email = '" + userRegister.Email + "'",conn);
            cmd0.CommandType = CommandType.Text;
            sqlDataAdapter sda = new sqlDataAdapter(cmd0);
            DataTable dt = new DataTable();
            sda.Fill(dt);

            if (dt.Rows.Count == 0)
            {
                if (!userRegister.Email.Equals("admin@skoola.com") && !userRegister.Password.Equals("123456"))
                {
                    userRegister.Role = "user";
                }
                else
                {
                    userRegister.Role = "admin";
                }

                DateTime datetime = DateTime.Now;
                userRegister.DateRegistered = datetime;

                sqlCommand cmd = new sqlCommand("spInsertUsers",conn);
                cmd.CommandType = CommandType.StoredProcedure;
                cmd.Parameters.AddWithValue("@Name",userRegister.Name);
                cmd.Parameters.AddWithValue("@IcNumber",userRegister.IcNumber);
                cmd.Parameters.AddWithValue("@Email",userRegister.Email);
                cmd.Parameters.AddWithValue("@Phone",userRegister.Phone);
                cmd.Parameters.AddWithValue("@Address1",userRegister.Address1);
                cmd.Parameters.AddWithValue("@Address2",userRegister.Address2);
                cmd.Parameters.AddWithValue("@Postcode",userRegister.Postcode);
                cmd.Parameters.AddWithValue("@City",userRegister.City);
                cmd.Parameters.AddWithValue("@Role",userRegister.Role);
                cmd.Parameters.AddWithValue("@DateRegistered",userRegister.DateRegistered);
                cmd.Parameters.AddWithValue("@Gender",userRegister.Gender);
                cmd.Parameters.AddWithValue("@Password",userRegister.Password);

 
                    if (conn.State == ConnectionState.Closed) { conn.open(); }
                    cmd.ExecuteNonQuery();
                    if (conn.State == ConnectionState.Open) { conn.Close(); }
                        Console.WriteLine("Saved");
                    //user.UserId = Convert.ToInt32(cmd.ExecuteScalar());
                    Session["Id"] = userRegister.Id;
                    Session["Name"] = userRegister.Name;
                    Session["IcNumber"] = userRegister.IcNumber;
                    Session["Email"] = userRegister.Email;
                    Session["Phone"] = userRegister.Phone;
                    Session["Address1"] = userRegister.Address1;
                    Session["Address2"] = userRegister.Address2;
                    Session["Postcode"] = userRegister.Postcode;
                    Session["City"] = userRegister.City;
                    Session["Role"] = userRegister.Role;
                    Session["DateRegistered"] = userRegister.DateRegistered;
                    Session["Gender"] = userRegister.DateRegistered;
                    Session["Password"] = userRegister.Password;
           
                return RedirectToAction("Login","User");
            }
            return View();
        }
        catch(Exception ex)
        {
            throw ex;
        }
    }