Question

我有一个简单的应用程序，它从数据库中读取以设置类中的属性，然后将结果集输出到屏幕以及写入文件。我正在尝试提前计划我的应用程序是一个Web应用程序，并希望它的设计尽可能接近最佳实践。我想知道我的DAL设计是否有任何重大缺陷，如果我从用户那里获取输入并将其设置为参数的方式是正常的，或者是否有更好的方法。程序中的所有内容都按预期工作。

DAL

public static List<Customers> GetCustomersByName()
        {
            //make the list of the type that the method will be returning
            List<Customers> c = new List<Customers>();
            //make a connection string variable
            string cs = ConfigurationManager.ConnectionStrings["dbcs"].ConnectionString;
            using (SqlConnection con = new SqlConnection(cs))
            {
                using(SqlCommand cmd = new SqlCommand("spFindCustomersByName",con))
                {
                    con.Open();
                    //this stored procedure has one input parameter, how do I send that to the data access layer?
                    cmd.CommandType = CommandType.StoredProcedure;
                    cmd.Parameters.Add("@lastName", SqlDbType.VarChar, 50);
                    //only way I could think of to get the value entered from a screen into 
                    //a parameter
                    cmd.Parameters["@lastName"].Value = Customers.AddSpParams();

                    //instantiate SqlDataReader
                    SqlDataReader rdr = cmd.ExecuteReader();
                    while(rdr.Read())
                    {
                        Customers custList = new Customers();
                        custList.CustomerId = Convert.ToInt32(rdr["customerId"]);
                        custList.LastName = rdr["lastName"].ToString();
                        custList.FirstName = rdr["firstName"].ToString();
                        custList.DateHired = (DateTime)rdr["dateHired"];
                        c.Add(custList);



                    }

                }
                return c;
            }

为存储过程的输入参数赋值的方法

public static string AddSpParams()
        {
            Console.Write("Search for a string in customer's name: ");
            string nameParam = Console.ReadLine();
            return nameParam;
        }

写入文本文件，写入控制台

static void Main(string[] args)
        {
            Console.WriteLine("This is only a test");
            List<Customers> c = DataAccessCustomers.GetCustomersByName();
            using (StreamWriter sw = new StreamWriter(@"C:\Users\customersList.txt"))
            {
                foreach(Customers custList in c)
                {
                    //write to console
                    Console.WriteLine(custList.CustomerId + "\t" + custList.FirstName + "\t" +
                        custList.LastName + "\t" + custList.DateHired);
                    //write to file
                    sw.WriteLine(custList.CustomerId + "\t" + custList.FirstName + "\t" +
                        custList.LastName + "\t" + custList.DateHired);
                }
            }
            Console.ReadLine();
        }

Answer 1

基本上，你的设计异常没有问题。我假设您的存储过程和Customer类不支持null值。所以，这里的主要缺陷是你的代码仍然没有处理DBNull值：

custList.LastName = rdr["lastName"].ToString();
custList.FirstName = rdr["firstName"].ToString();
custList.DateHired = (DateTime)rdr["dateHired"];

在调用.ToString()或装箱(DateTime)rdr["dateHired"];之前，您应该检查rdr [“lastName”]和rdr [“firstName”]的DBNull值希望这有帮助。

在数据访问层中使用存储过程

1 个答案: