小弟最近看了一段程序
 namespace bookmis
{
    public partial class logon : Form
    {
        public logon()
        {
            InitializeComponent();
        }

        private void btnlogon_Click(object sender, EventArgs e)
        {
            SqlConnection sqlcon = new SqlConnection("data source=localhost;Initial catalog=Bookstore;Integrated security=sspi;");

            string str = "insert into dbo.读者 values(@loginname,@loginpassword)";//这两个是哪里来的啊
            sqlcon.Open();
            SqlCommand cmd = new SqlCommand(str, sqlcon);
            cmd.Parameters.Add("@loginname", SqlDbType.NChar, 20);
            cmd.Parameters.Add("@loginpassword", SqlDbType.NChar, 20);
            cmd.Parameters["@loginname"].Value = tBoxuser.Text;
            cmd.Parameters["@loginpassword"].Value = tBoxpassword.Text;
            cmd.ExecuteNonQuery();
            sqlcon.Close();
            MessageBox.Show("注册成功");
            this.tBoxuser.Clear();
            this.tBoxpassword.Clear();
        }
    }
}
怎么会连不上数据库呢，不显示messagebox啊，数据库名bookstore，表名读者，步骤好像也对，可就是点了button没反应。谁能指教一下啊
还有 cammand对象的 paramerers 方法什么意思啊  怎么使用啊 请指教一下

string connestring = "Data Source=WIN-08OC9UFPA79;Initial Catalog=school1;Integrated Security=True";
        SqlConnection connection;
        SqlCommand command;
connection = new SqlConnection(connestring);
 connection.Open();
 string str = "insert into dbo.读者 values(@loginname,@loginpassword)";//这两个是哪里来的啊 dbo.读者这个表里的两个属性！
 SqlCommand cmd = new SqlCommand(str, sqlcon);//执行命令，也就是SQL语句；

string connestring = "Data Source=.;Initial Catalog=bookstore;Integrated Security=True";
        SqlConnection connection;
        SqlCommand command;
connection = new SqlConnection(connestring);
connection.Open();
string str = "insert into dbo.读者 values(@loginname,@loginpassword)";
SqlCommand cmd = new SqlCommand(str, sqlcon);

cmd.Parameters.Add("@loginname", SqlDbType.NChar, 20);
            cmd.Parameters.Add("@loginpassword", SqlDbType.NChar, 20);
            cmd.Parameters["@loginname"].Value = tBoxuser.Text;
            cmd.Parameters["@loginpassword"].Value = tBoxpassword.Text;
            cmd.ExecuteNonQuery();
            sqlcon.Close();
            MessageBox.Show("注册成功");
            this.tBoxuser.Clear();
            this.tBoxpassword.Clear();