อยากรบกวน ถาม โค๊ด generate number แบบรันไปเรื่อยๆอะคะ

 public string GetId(string pname)
        {

            Conn = new SqlConnection();
            if (Conn.State == ConnectionState.Open)
            {
                Conn.Close();
            }
            Conn.ConnectionString = DBConnString.strConn;
            Conn.Open();

            string pid;
            string strSql = "SELECT max(right(packing_no,7))+1 as id FROM PICKING" ;
            int x;
            com = new SqlCommand();
            com.CommandType = CommandType.Text;
            com.CommandText = strSql;
            com.Connection = Conn;
            dr = com.ExecuteReader();
            DataTable dt = new DataTable();
            if (dr.HasRows)
            {
                dt.Load(dr);
            }
            dr.Close();
            Conn.Close();
            try
            {
                x = Convert.ToInt32(dt.Rows[0]["id"]);
            }
            catch
            {
                x = 1;
            }
            pid = x.ToString("0000000");
            pid = pname + pid;
            return pid;

        }

 txtBox_GenPickNO.text= GetId("P10");

public string GetId(string pname)
{
DbProviderFactory factory = DbProviderFactories.GetFactory("System.Data.SqlClient"); 
IDbConnection con = factory.CreateConnection();
con.ConnectionString = ConfigurationManager.ConnectionStrings["dbInvoice"].ToString();
IDbCommand com = factory.CreateCommand(); 
com.Connection = con;
con.Open();
string pid;
string strSql = "SELECT max(right(packing_no,7))+1 as id FROM PICKING" ;
int x;
com = new SqlCommand();
com.CommandType = CommandType.Text;
com.CommandText = strSql;
com.Connection = con;
dr = com.ExecuteReader();
DataTable dt = new DataTable();
if (dr.HasRows)
{
dt.Load(dr);
}
dr.Close();
con.Close();
try
{
x = Convert.ToInt32(dt.Rows[0]["id"]);
}
catch
{
x = 1;
}
pid = x.ToString("0000000");
pid = pname + pid;
return pid;

}