ช่วยหน่อยครับ Error : object reference not set to an instance of an object

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Data.SqlClient;
using System.Text;
using System.IO;
using System.Data.Sql;
using System.Configuration;
using System.Net;
using System.Web.Security;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;

namespace ECN_Dev
{
    public class matchControl
    {
        SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["Sql"].ConnectionString);
        string sqlstr;
        datacls dc = new datacls();
        protected string MatchSQL(string showon)
        {
            string str;
            str = "select * from match_control as t1 inner join show_control as t2 on t1.m_fields=t2.m_fields where  c_showon like '" + showon + "'  order by c_order";

            return str;

        }
        public void toControl(string showon, GridView GV)
        {


            dc.QryDT(conn, MatchSQL(showon));
            if (dc.dt.Rows.Count > 0)
            {
                foreach (DataRow dr in dc.dt.Rows)
                {
                    BoundField bf = new BoundField();
                    bf.DataField = dr["m_fields"].ToString();
                    bf.HeaderText = dr["m_des"].ToString();
                    if (dr["m_ftype"].ToString() == "date") { bf.DataFormatString = "{0:MM/dd/yyyy}"; }

                    GV.Columns.Add(bf);

                }
            }
        }


        public DataTable CreateDT(string showon)
        {
            DataTable dt = new DataTable(showon);

            dc.QryDT(conn, MatchSQL(showon));
            if (dc.dt.Rows.Count > 0)
            {
                foreach (DataRow dr in dc.dt.Rows)
                {

                    DataColumn dtc = new DataColumn((string)dr["m_fields"]);
                    dt.Columns.Add(dtc);



                }
            }


            return dt;



        }

        public string SelectbyOrder(string showon)
        {
            string str = "";
            dc.QryDT(conn, MatchSQL(showon));
            if (dc.dt.Rows.Count > 0)
            {
                foreach (DataRow dr in dc.dt.Rows)
                {
                    str += "," + dr["m_fields"].ToString();
                }

            }
            str = str.Substring(1);
            return str;
        }



        public DataRow addRow(string showon, DataTable dt, ContentPlaceHolder me, string key)
        {


            DataRow dr = dt.NewRow();
            dc.QryDT(conn, MatchSQL(showon));
            if (dc.dt.Rows.Count > 0)
            {
                foreach (DataRow dr1 in dc.dt.Rows)
                {

                    if (!key.Contains(dr1["m_fields"].ToString()))
                    {
                        string str = getString(me.FindControl((string)dr1["m_con"]));
                        if (dr1["m_ftype"].ToString() == "date" && str == "")
                            dr[dr1["m_fields"].ToString()] = DBNull.Value;
                        else
                            dr[dr1["m_fields"].ToString()] = str;
                    }
                }

            }

            return dr;

        }

        protected string getString(Control ctrl)
        {
            string result;

            if (ctrl.GetType() == typeof(TextBox)) result = ((TextBox)ctrl).Text;
            else if (ctrl.GetType() == typeof(DropDownList)) result = ((DropDownList)ctrl).SelectedValue;
            else if (ctrl.GetType() == typeof(RadioButtonList)) result = ((RadioButtonList)ctrl).SelectedValue;
            else if (ctrl.GetType() == typeof(Label)) result = ((Label)ctrl).Text;
            else result = "";

            return result;
        }

        public void GVrowtocon(string showon, GridViewRow row, ContentPlaceHolder me)
        {


            dc.QryDT(conn, MatchSQL(showon));
            if (dc.dt.Rows.Count > 0)
            {
                for (int i = 0; i < dc.dt.Rows.Count; i++)
                {


                    setCtrl(me.FindControl((string)dc.dt.Rows[i]["m_con"]), Modcls.Nullnbsp(row.Cells[i + 1].Text));

                }
            }
        }

        protected void setCtrl(Control ctrl, string value)
        {

            if (ctrl.GetType() == typeof(TextBox))
            {
                ((TextBox)ctrl).Text = value;
            }
            else if (ctrl.GetType() == typeof(DropDownList))
            {
                ((DropDownList)ctrl).SelectedValue = value;
            }
            else if (ctrl.GetType() == typeof(RadioButtonList))
            {
                ((RadioButtonList)ctrl).SelectedValue = value;
            }
        }

        public void DTrowtocon(string showon, DataTable iDT, ContentPlaceHolder me)
        {


            dc.QryDT(conn, MatchSQL(showon));
            if (dc.dt.Rows.Count == 0) return;

            foreach (DataRow dr in dc.dt.Rows)
            {


                if (dr["m_ftype"].ToString() == "date")
                    setCtrl(me.FindControl((string)dr["m_con"]), Modcls.ConvertDate(iDT.Rows[0][dr["m_fields"].ToString()].ToString()));
                else
                    setCtrl(me.FindControl((string)dr["m_con"]), iDT.Rows[0][dr["m_fields"].ToString()].ToString());


            }
        }



        public void updateSQL(string Table, string showon, ContentPlaceHolder me, string Key, string ExStr = "")
        {
            string wheresql = "", rowsql = "";
            dc.QryDT(conn, MatchSQL(showon));
            if (dc.dt.Rows.Count > 0)

                sqlstr = " begin ";

            sqlstr += "update " + Table + " set ";


            foreach (DataRow dr in dc.dt.Rows)
            {

                if (!Key.Contains(dr["m_fields"].ToString()))
                {
                    if (dr["m_ftype"].ToString() == "date")
                        rowsql += "," + dr["m_fields"] + "=" + Modcls.NullDate(getString(me.FindControl((string)dr["m_con"]))) + "";
                    else
                        rowsql += "," + dr["m_fields"] + "='" + getString(me.FindControl((string)dr["m_con"])) + "'";
                }
                else
                {

                    //string[] KeyArr = Key.Split(',');
                    // foreach (string iKey in KeyArr)
                    //{
                    wheresql += "and " + dr["m_fields"] + " like '" + getString(me.FindControl((string)dr["m_con"])) + "'";
                    //}

                }
            }
            wheresql = wheresql.Substring(3);
            wheresql = " where " + wheresql;
            rowsql = rowsql.Substring(1);
            sqlstr += rowsql + ExStr + wheresql;




            sqlstr += " end ";


            dc.RunCommand(conn, sqlstr);
        }





        public void inserSQLGV(string Table, string showon, ContentPlaceHolder me, GridView gv1, string key)
        {



            dc.QryDT(conn, MatchSQL(showon));
            if (dc.dt.Rows.Count == 0) return;
            if (gv1.Rows.Count == 0) return;

            for (int i = 0; i < gv1.Rows.Count; i++)
            {

                sqlstr = " begin ";
                sqlstr += "insert into " + Table + "(";
                string fsql = "", vsql = "";
                foreach (DataRow dr in dc.dt.Rows)
                {
                    if (!key.Contains(dr["m_fields"].ToString()))
                    {
                        fsql += ",[" + dr["m_fields"] + "]";
                        if (dr["c_ongv"].ToString() != "")
                        {
                            if (dr["m_ftype"].ToString() == "date")

                                vsql += "," + Modcls.NullDate(gv1.Rows[i].Cells[(int)dr["c_order"]].Text) + "";
                            else
                                vsql += ",'" + Modcls.Nullnbsp(gv1.Rows[i].Cells[(int)dr["c_order"]].Text) + "'";
                        }
                        else
                        {

                            if (dr["m_ftype"].ToString() == "date")
                                vsql += "," + Modcls.NullDate(getString(me.FindControl((string)dr["m_con"]))) + "";
                            else
                                vsql += ",'" + Modcls.Nullnbsp(getString(me.FindControl((string)dr["m_con"]))) + "'";
                        }
                    }
                }
                vsql = vsql.Substring(1);
                fsql = fsql.Substring(1);

                sqlstr += fsql + ") values(" + vsql + ") end";
                dc.RunCommand(conn, sqlstr);

            }

        }

    }

}