รบกวนช่วยดูโค้ด Error .NET ด้วยค่ะ ทำบน Sharepoint นะ

using Microsoft.Office.InfoPath;
using System;
using System.Xml;
using System.Xml.XPath;
using System.Data;
using System.Data.SqlClient;
using System.IO;

namespace RequestForm
{
    public partial class FormCode
    {
        DBConnect DB = new DBConnect();

        // Member variables are not supported in browser-enabled forms.
        // Instead, write and read these values from the FormState
        // dictionary using code such as the following:
        //
        // private object _memberVariable
        // {
        //     get
        //     {
        //         return FormState["_memberVariable"];
        //     }
        //     set
        //     {
        //         FormState["_memberVariable"] = value;
        //     }
        // }

        // NOTE: The following procedure is required by Microsoft InfoPath.
        // It can be modified using Microsoft InfoPath.
        public void InternalStartup()
        {
            EventManager.XmlEvents["/my:myFields/my:abFromDate"].Changed += new XmlChangedEventHandler(abFromDate_Changed);
            EventManager.XmlEvents["/my:myFields/my:abEndDate"].Changed += new XmlChangedEventHandler(abEndDate_Changed);
        }

        public void abFromDate_Changed(object sender, XmlEventArgs e)
        {
            // Write your code here to change the main data source.
            XPathNavigator nav = MainDataSource.CreateNavigator();

            string aFromDate = nav.SelectSingleNode("//my:abFromDate", NamespaceManager).Value;

            string aEndDate = nav.SelectSingleNode("//my:abEndDate", NamespaceManager).Value;

            String strSQL;
            DataSet ds;
            strSQL = "SELECT Count(*) HDate FROM Holidays where HolidaysDate between '" + aFromDate + "' AND '" + aEndDate + "'";
            ds = DB.QueryDataSet(strSQL);

            string x = ds.Tables[0].Rows[0][0].ToString();

            DB.Close();


            //-----------------
            strSQL = "select datediff(day,'" + aFromDate + "','" + aEndDate + "') as DateDD";
            ds = DB.QueryDataSet(strSQL);

            string y = ds.Tables[0].Rows[0][0].ToString();

            DB.Close();

            int xx = Convert.ToInt32(y) - Convert.ToInt32(x);

            nav.SelectSingleNode("//my:abTotalDate", NamespaceManager).SetValue(xx.ToString()); 
        }

        public void abEndDate_Changed(object sender, XmlEventArgs e)
        {
            // Write your code here to change the main data source.
            XPathNavigator nav = MainDataSource.CreateNavigator();

            string aFromDate = nav.SelectSingleNode("//myFields:abFromDate", NamespaceManager).Value;

            string aEndDate = nav.SelectSingleNode("//myFields:abEndDate", NamespaceManager).Value;

            String strSQL;
            DataSet ds;
            strSQL = "SELECT Count(*) HDate FROM Holidays where HolidaysDate between '" + aFromDate + "' AND '" + aEndDate + "'";
            ds = DB.QueryDataSet(strSQL);

            string x = ds.Tables[0].Rows[0][0].ToString();

            DB.Close();


            //-----------------
            strSQL = "select datediff(day,'" + aFromDate + "','" + aEndDate + "') as DateDD";
            ds = DB.QueryDataSet(strSQL);

            string y = ds.Tables[0].Rows[0][0].ToString();

            DB.Close();

            int xx = Convert.ToInt32(y) - Convert.ToInt32(x);

            nav.SelectSingleNode("//myFields:abTotalDate", NamespaceManager).SetValue(xx.ToString()); 
        }
    }
}

using System;
using System.Collections.Generic;
using System.Text;
using System.Data.SqlClient;
using System.Data;

namespace RequestForm
{
    class DBConnect
    {
        private SqlConnection objConn;
        private SqlCommand objCmd;
        private SqlTransaction Trans;
        private String strConnString;
        private String strCommandString;

        public DBConnect()
        {
            strConnString = "Server=192.168.1.2;Database=HR;Trusted_Connection=True;";
        }

        public SqlDataReader QueryDataReader(String strSQL)
        {
            SqlDataReader dtReader;
            objConn = new SqlConnection();
            objConn.ConnectionString = strConnString;
            objConn.Open();

            objCmd = new SqlCommand(strSQL, objConn);
            dtReader = objCmd.ExecuteReader();
            return dtReader; //*** Return DataReader ***//
        }

        public DataSet QueryDataSet(String strSQL)
        {
            DataSet ds = new DataSet();
            SqlDataAdapter dtAdapter = new SqlDataAdapter();
            objConn = new SqlConnection();
            objConn.ConnectionString = strConnString;
            objConn.Open();

            objCmd = new SqlCommand();
            objCmd.Connection = objConn;
            objCmd.CommandText = strSQL;
            objCmd.CommandType = CommandType.Text;

            dtAdapter.SelectCommand = objCmd;
            dtAdapter.Fill(ds);
            return ds;   //*** Return DataSet ***//
        }

        public DataTable QueryDataTable(String strSQL)
        {
            SqlDataAdapter dtAdapter;
            DataTable dt = new DataTable();
            objConn = new SqlConnection();
            objConn.ConnectionString = strConnString;
            objConn.Open();

            dtAdapter = new SqlDataAdapter(strSQL, objConn);
            dtAdapter.Fill(dt);
            return dt; //*** Return DataTable ***//
        }

        public Boolean QueryExecuteNonQuery(String strSQL)
        {
            objConn = new SqlConnection();
            objConn.ConnectionString = strConnString;
            objConn.Open();

            try
            {
                objCmd = new SqlCommand();
                objCmd.Connection = objConn;
                objCmd.CommandType = CommandType.Text;
                objCmd.CommandText = strSQL;

                objCmd.ExecuteNonQuery();
                return true; //*** Return True ***//
            }
            catch (Exception)
            {
                return false; //*** Return False ***//
            }
        }


        public Object QueryExecuteScalar(String strSQL)
        {
            Object obj;
            objConn = new SqlConnection();
            objConn.ConnectionString = strConnString;
            objConn.Open();

            try
            {
                objCmd = new SqlCommand();
                objCmd.Connection = objConn;
                objCmd.CommandType = CommandType.Text;
                objCmd.CommandText = strSQL;

                obj = objCmd.ExecuteScalar();  //*** Return Scalar ***//
                return obj;
            }
            catch (Exception)
            {
                return null; //*** Return Nothing ***//
            }
        }

        public void TransStart()
        {
            objConn = new SqlConnection();
            objConn.ConnectionString = strConnString;
            objConn.Open();
            Trans = objConn.BeginTransaction(IsolationLevel.ReadCommitted);
        }


        public void TransExecute(String strSQL)
        {
            objCmd = new SqlCommand();
            objCmd.Connection = objConn;
            objCmd.Transaction = Trans;
            objCmd.CommandType = CommandType.Text;
            objCmd.CommandText = strSQL;
            objCmd.ExecuteNonQuery();
        }


        public void TransRollBack()
        {
            Trans.Rollback();
        }

        public void TransCommit()
        {
            Trans.Commit();
        }

        public void Close()
        {
            objConn.Close();
            objConn = null;
        }

        public string CommandString
        {
            get
            {
                return strCommandString;
            }
            set
            {
                strCommandString = value;
                objConn = new SqlConnection();
                objConn.ConnectionString = strConnString;
                objCmd = new SqlCommand(strCommandString, objConn);
            }
        }

        public void AddParameter(string ParameterName, object ParameterValue)
        {
            objCmd.Parameters.AddWithValue(ParameterName, ParameterValue);
        }

        public bool ExecuteNonQuery()
        {
            int rowsAffected = 0;

            try
            {
                objConn.Open();
                rowsAffected = objCmd.ExecuteNonQuery();
                objConn.Close();
            }
            catch (Exception)
            {
                rowsAffected = 0;
            }

            return (rowsAffected > 0) ? true : false;
        }
    }
}