แก้ error Table = null ค่ะ มีวิธีแก้ไหมค่ะ กรณีที่ ตารางยังไม่มีข้อมูลค่ะ

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace WebApplication3.Training
{
    public partial class New_Training : System.Web.UI.Page
    {
        clsDatabase dbconn = new clsDatabase();

        protected void Page_Load(object sender, EventArgs e)
        {

        }

  
        protected void btnConfirm_Click(object sender, EventArgs e)
        {

            string findmax = "SELECT max(Activity_ID) FROM [Activities]";

            object obj = dbconn.QueryExecuteScalar(findmax);

            [font=Verdana]string objString = (string)obj;[/font]
            int yearMax = Convert.ToInt32(objString.Substring(1, 4));

            int idMax = Convert.ToInt32(objString.Substring(4).Trim());

            if (idMax == null)
            {
                idMax = 0;
            }

            int yearNow = Convert.ToInt32(DateTime.Now.ToString("yyyy"));

            string nextID = (idMax + 1).ToString().PadLeft(3, '0');

            if (yearMax != yearNow)
            {
                nextID = "001";
            }

            string year = DateTime.Now.ToString("yyyy");
            int year1 = Convert.ToInt32(year);
            int thaiyear = year1;
            string newid = thaiyear + nextID;

                     
            string SqlAddTraining;
            SqlAddTraining = "insert into Activities (Activity_ID, AT_ID, Activity_Name, Activity_StartDate,Activity_EndDate, Activity_Place, Activity_Province,Activity_Status) Values('"+newid+"','2','"+txtTrainingName.Text+"','"+dbpStartDate.Text+"','"+bdpEnddate.Text+"','"+txtTrainingPlace.Text+"','"+ddlProvince.SelectedValue+"','Starting');";
            
        
        }
    }
}