When I Select Option From Dropdown And Click On Add At That Time It Will Show Error-Can Not Find Table

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.Configuration;

namespace SMSReminderProject
{
    public partial class pgTemplateMaster : System.Web.UI.Page
    {
        static int wl_TemDID = 0;
        //static int wl_TH = 0;
        int i = 0;
        string lsQuery;
        static string constr = ConfigurationManager.ConnectionStrings["conster"].ToString();
        SqlConnection conn = new SqlConnection(constr);

        DataSet dtItems = new DataSet();
        
    
        protected void Page_Load(object sender, EventArgs e)
        {
         
             fill_grdtemplatemasterHeader();
            ViewState["dtItems"] = dtItems;
            BindGrid();

            if (!IsPostBack)
            {

                FillddlOperator();
                datatable();
                //datatable();
              
            }


        }


        private void FillddlOperator()
        {

            string lsquery;
        
            lsquery = "select opID,opName  from [tbl_operator]";
            SqlCommand select = new SqlCommand(lsquery, conn);
            SqlDataAdapter DA = new SqlDataAdapter(select);
            DataTable dt = new DataTable();

            conn.Open();
            select.ExecuteNonQuery();
            DA.Fill(dt);

            ddlOperator.DataSource = dt;
            ddlOperator.DataValueField = "opID";
            ddlOperator.DataTextField = "opName";

            ddlOperator.DataBind();
            ddlOperator.Items.Insert(0, new ListItem("--Select--", "0"));
            ddlOperator.SelectedIndex = 0;
            conn.Close();

        }
        public void datatable()
        {

            //DataTable CreateDataTable()
            DataTable ordersTable = dtItems.Tables.Add("Orders");
            //DataTable dtItems = new DataTable();

            //Add Auto No. Column to the DataTable
            dtItems.Tables[0].Columns.Add("StaticId", typeof(int));
            dtItems.Tables[0].PrimaryKey = new DataColumn[] { dtItems.Tables[0].Columns["StaticId"] };
            dtItems.Tables[0].Columns["StaticId"].AutoIncrement = true;
            dtItems.Tables[0].Columns["StaticId"].AutoIncrementSeed = 1;
           


            //Add three more columns to the DataTable
            dtItems.Tables[0].Columns.Add("TemDID", typeof(int));
            dtItems.Tables[0].Columns["TemDID"].DefaultValue = 0;

            dtItems.Tables[0].Columns.Add("TemHID", typeof(int));
            dtItems.Tables[0].Columns["TemHID"].DefaultValue = 0;

            dtItems.Tables[0].Columns.Add("opID", typeof(int));
            dtItems.Tables[0].Columns["opID"].DefaultValue = 0;

            dtItems.Tables[0].Columns.Add("opName", typeof(string));
            dtItems.Tables[0].Columns["opName"].ToString();

            dtItems.Tables[0].Columns.Add("IsActive", typeof(Boolean));

            dtItems.Tables[0].Columns.Add("IsDeleted", typeof(Boolean));
        
            //rupal comment
            //dtItems.Tables[0].Rows.Add(dtItems.Tables[0].NewRow());
            dtItems.Tables[0].AcceptChanges();

            ViewState["dtItems"] = dtItems;
            wp_Filltemplatedetail();

            //dtItems.Tables("IsDeleted").DefaultView.RowFilter = "";
            //ViewState["dtItems"] = dtItems;

        }

        public void wp_Filltemplatedetail()
        {
            //DataTable dtItems = new DataTable();
            dtItems.Tables[0].Columns["IsDeleted"].DefaultValue = "false";
            grdTemplateDetail.DataSource = dtItems.Tables[0];
            //grdTemplateDetail.DataSource = ViewState["dtItems"] as DataTable;
            grdTemplateDetail.DataBind();
        }
        public void btnAdd_Click(object sender, EventArgs e)
        {

            dtItems = (DataSet)ViewState["dtItems"];
            DataRow dr = dtItems.Tables[0].NewRow();


            dr["TemDID"] = 0;
            dr["TemHID"] = 0;
            dr["opID"] = ddlOperator.SelectedValue;
            dr["opName"] = ddlOperator.SelectedItem;
            dr["IsActive"] = chkIsActive.Checked;
            dtItems.Tables[0].Rows.Add(dr);
            dtItems.AcceptChanges();
            ViewState["dtItems"] = dtItems;
         
            grdTemplateDetail.DataSource = ViewState["dtItems"];
            grdTemplateDetail.DataBind();
            ddlOperator.Items.Insert(0, new ListItem("--Select--", "0"));
            ddlOperator.SelectedIndex = 0;

        }

       


        protected void grdtemplatemasterHeader_SelectedIndexChanged(object sender, EventArgs e)
        {

        }



        private void fill_grdtemplatemasterHeader()
        {
            string lsquery;
            lsquery = "select TOP 10 * from tbl_Template_H ORDER BY TemHID desc";
            SqlCommand select = new SqlCommand(lsquery, conn);
            SqlDataAdapter DA = new SqlDataAdapter(select);
            DataTable dt = new DataTable();

            conn.Open();
            select.ExecuteNonQuery();
            DA.Fill(dt);
            grdtemplatemasterHeader.DataSource = dt;
            grdtemplatemasterHeader.DataBind();

            conn.Close();

        }

       

        private void wp_Clear()
        {
            txtTemplate.Text = "";
        }

        protected void btnSave_Click(object sender, EventArgs e)
        {
            int iThID = 0;
           

            iThID = ExecuteQuery("insert into tbl_Template_H(TemHName,TemHActive) values('" + txtTemplate.Text + "' ,'" + chkIsActive.Checked + "')");

            dtItems = ((DataSet)ViewState["dtItems"]).Copy();
            //foreach (DataRow dr in dtItems.Tables[0].Rows )
            foreach (DataRow dr in dtItems.Tables[0].Rows)
                {
                    if ((bool)dr["IsDeleted"] == false)
                    //if((int)dr["IsDeleted"]== 0)
                             
                    {
                         ExecuteQuery("insert into tbl_Template_D(TemHID,opID) values(" + iThID + "," + (dr["opID"])  + "   )");
                    }


                    fill_grdtemplatemasterHeader();
                    wp_Clear();
                   
                }

         
      


       
        }

        // added by Mayur on 28 apr 2015
        protected Int32 ExecuteQuery(string Query)
        {
            int li_ID;
            SqlCommand cmd = new SqlCommand(Query, conn);
            conn.Open();
            cmd.ExecuteNonQuery();
            cmd.CommandText = "SELECT @@IDENTITY";
            li_ID =System.Convert.ToInt32 (cmd.ExecuteScalar());
            //li_ID = (Int32)cmd.ExecuteScalar();
            conn.Close();
           return li_ID;
        }
       
      



        //http://www.aspnettutorials.com/tutorials/database/add-data-to-gridview-from-multiple-tables-in-asp-net-4-0-and-c/
        //http://www.aspnettutorials.com/tutorials/controls/data-table-csharp/

        protected DataTable ExecuteDT1(string Query)
        {
          
            DataTable dt1 = new DataTable();
            i = Convert.ToInt16(txtTemDID.Text);

            SqlDataAdapter adp = new SqlDataAdapter(Query, conn);
            adp.Fill(dt1);
            grdTemplateDetail.DataSource = dt1;
            grdTemplateDetail.DataBind();
            return dt1;
        }
        protected void BindGrid()
        {
            //grdTemplateDetail.DataSource = ViewState["dt"] as DataTable;
            //grdTemplateDetail.DataBind();
            grdTemplateDetail.DataSource =ViewState["dtItems"] as DataTable;
            grdTemplateDetail.DataBind();
        }
        protected void grdTemplateDetail_DataBound(object sender, GridViewRowEventArgs e)
        {
            if (e.Row.RowType == DataControlRowType.DataRow)
            {
                if (((CheckBox)(e.Row.Cells[0].Controls[0])).Checked)
                {
                    e.Row.BackColor = System.Drawing.Color.Yellow;
                }
            }
        }
        protected void grdTemplateDetail_RowDeleting(object sender, GridViewDeleteEventArgs e)
        {
           
            
        }

        protected void grdTemplateDetail_SelectedIndexChanged(object sender, EventArgs e)
        {
            i = Convert.ToInt16(txtTemDID.Text);
           
           
        }


        
        //mayur sir
        protected DataTable ExecuteDT(string Query)
        {
            DataTable dt = new DataTable();
            i = Convert.ToInt16(txtTemHID.Text);
            SqlDataAdapter adp = new SqlDataAdapter(Query, conn);
            adp.Fill(dt);
            grdTemplateDetail.DataSource = dt;
            grdTemplateDetail.DataBind();
            return dt;

           
        }
        protected void grdtemplatemasterHeader_SelectedIndexChanged1(object sender, EventArgs e)
        {
           
            txtTemHID.Text = grdtemplatemasterHeader.SelectedRow.Cells[1].Text;
            i = Convert.ToInt16(txtTemHID.Text);
            txtTemplate.Text = grdtemplatemasterHeader.SelectedRow.Cells[2].Text;

           
            ExecuteDT("select tbl_Template_D.TemHID,tbl_Template_D.TemDID, tbl_Template_D.opID  from tbl_Template_D left join tbl_Template_H on tbl_Template_D.TemHID = tbl_Template_H.TemHID where tbl_Template_H.TemHID=" + txtTemHID.Text + "");
          
                       
           
        }

       

      

       

    }

}