空连接 - 连接到ASP.NET - Microsoft SQL Server

Question

我一直在尝试连接数据库,但它显示'null'错误.所以,我尝试打开我练习的上一个表格,结果证明是完美的.

这是我的代码:

string username = txtusername.Text;
        string firstname = txtfirstname.Text;
        string lastname = txtlastname.Text;
        string email = txtemail.Text;
        string password = txtpass.Text;
        string gender = rbgender.Text;
        string nationality = dcountry.Text;
        string phone = txtphone.Text;

        string connection = ConfigurationManager.ConnectionStrings["connectionString"].ConnectionString;
        SqlConnection connect = new SqlConnection(connection);
        string command = "INSERT INTO Persons(username, firstname, lastname, email, password, gender, nationality, phone) VALUES('@username','@firstname','@lastname','@email','@password','@gender','@nationality','@phone')";


        SqlCommand insert = new SqlCommand(command +","+ connection);
        insert.Parameters.AddWithValue("@username", username);
        insert.Parameters.AddWithValue("@firstname", firstname);
        insert.Parameters.AddWithValue("@lastname", lastname);
        insert.Parameters.AddWithValue("@email", email);
        insert.Parameters.AddWithValue("@password", password);
        insert.Parameters.AddWithValue("@gender", gender);
        insert.Parameters.AddWithValue("@nationality", nationality);
        insert.Parameters.AddWithValue("@phone", phone);
        insert.ExecuteNonQuery();
        connect.Close();

它与web.config中的连接字符串有什么关系吗？

 <connectionStrings>
<add name="ApplicationServices"
     connectionString="Data Source=ADRIAN-LAPTOP\SQL;Initial Catalog=New;Integrated Security=True"
     providerName="System.Data.SqlClient" />

Answer 1

密钥web.config文件不同,然后在代码中使用.

它应该是,

string connection = ConfigurationManager.ConnectionStrings["ApplicationServices"]
                                        .ConnectionString;

并且无需在单引号中包装参数名称.

 string command = @"
   INSERT INTO Persons
      (username, firstname, lastname, email, password, gender, nationality,phone) 
     VALUES
      (@username,@firstname,@lastname,@email,@password,@gender,@nationality,@phone)";

附注,始终使用using语句(或调用Dispose())来处置ADO资源.

using(SqlConnection connect = new SqlConnection(connectionString))
 {
  //
 }