用存储过程添加记录的问题，急，，，，，，

ALTER proc [dbo].[insertuser]
(
@username NVarChar(50),
@userpw NVarChar(50),
@usertel NVarChar(50),
@usermail NVarChar(50),
@userqq nchar(10),
@userip NVarChar(50),
@userquanxian nchar(10),
@adddatetime DateTime
)
As
Insert Into hluser(username,userpw,usertel,usermail,userqq,userip,userquanxian,adddatetime) Values (@username,@userpw,@usertel,@usermail,@userqq,@userip,@userquanxian,@adddatetime)
---------------------------------------------------------------------
 string username = this.txtuname.Text;
            string userpw = this.txtuserpassword.Text;
            string usermob = this.txttelephone.Text;
            string usermail = this.txtemail.Text;
            string userqq = this.txtqq.Text;
            string userip = Request.UserHostAddress;
            string userqx = "1";
            DateTime usernow = DateTime.Now;            System.Security.Cryptography.MD5 md5 = new System.Security.Cryptography.MD5CryptoServiceProvider();
            userpw = System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(userpw.ToString(), "md5");            try
            {
                SqlDbConnection mydb = new SqlDbConnection();
                mydb.conn.Open();
                SqlCommand cmd = new SqlCommand("insertuser", mydb.conn);
                cmd.CommandType = CommandType.StoredProcedure;
                cmd.Parameters.Add("@username", SqlDbType.NVarChar, 50);
                cmd.Parameters.Add("@userpw", SqlDbType.NVarChar, 50);
                cmd.Parameters.Add("@usertel", SqlDbType.NVarChar, 50);
                cmd.Parameters.Add("@usermail", SqlDbType.NVarChar, 50);
                cmd.Parameters.Add("@userqq", SqlDbType.NChar, 10);
                cmd.Parameters.Add("@userip", SqlDbType.NVarChar, 50);
                cmd.Parameters.Add("@userquanxian", SqlDbType.NChar, 10);
                cmd.Parameters.Add("@adddatetime", SqlDbType.DateTime);                cmd.Parameters["@username"].Value = username.ToString();
                cmd.Parameters["@userpw"].Value = userpw;
                cmd.Parameters["@usertel"].Value = usermob.ToString();
                cmd.Parameters["@usermail"].Value = usermail.ToString();
                cmd.Parameters["@userqq"].Value = userqq.ToString();
                cmd.Parameters["@userip"].Value = userip.ToString();
                cmd.Parameters["@userquanxian"].Value = userqx.ToString();
                cmd.Parameters["@adddatetime"].Value = usernow;
                cmd.ExecuteNonQuery();
                //cmd.Dispose();
                //mydb.conn.Close();
            }
            catch
            {
                Response.Write("数据连接已断开，注册失败，请和系统管理员联系！");
                return;
            }--------------------------------------------------------------------------------无法添加记录，报"数据连接已断开，注册失败，请和系统管理员联系！"
请大侠们帮忙看下怎么改好。。谢谢。。急死了。