DBConnector:

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


namespace ShareLibrary.DAL
{
   public class DBConnector
    {
        private string connectionString = null;
        private SqlConnection sqlConn = null;

        public DBConnector()
        {
            connectionString = ConfigurationManager.ConnectionStrings["ShareDBConnectionString"].ToString();

            sqlConn = new SqlConnection(connectionString);
        }

        ///

        /// Return sqlConnection
        ///

        public SqlConnection GetConnection
        {
            get
            {
                return sqlConn;
            }

        }
    }
}


Insert Class:

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

namespace ShareLibrary.DAL.Gateways
{
   public class DataInsertion
    {
        #region Member variables

        private DBConnector dbConnectorObject;
        private SqlConnection sqlConnectionObject;

        #endregion

        #region Execute query and insert data

        ///

        /// Insert data to database
        ///

        ///
Query striing
        ///
        public bool InsertData(string sqlString)
        {

            dbConnectorObject = new DBConnector();
            sqlConnectionObject = new SqlConnection();
            sqlConnectionObject = dbConnectorObject.GetConnection;

            try
            {
                sqlConnectionObject.Open();
                SqlCommand sqlCommandObject = new SqlCommand(sqlString, sqlConnectionObject);

                int i = sqlCommandObject.ExecuteNonQuery();
                if (i > 0)
                    return true;
                else
                    return false;
            }

            catch (SqlException ex)
            {
                throw new Exception(" Database problem.\n" + ex.Message);
            }

            finally
            {
                if (sqlConnectionObject.State == ConnectionState.Open)
                {
                    sqlConnectionObject.Close();
                }
            }
        }


        #endregion

        #region insert method with parameter
        ///

        /// this method insert data into database
        ///

        /// Query string
        /// Sql parameter
        ///
        public bool InsertData(string sqlString, List parametersList)
        {
            dbConnectorObject = new DBConnector();
            sqlConnectionObject = new SqlConnection();
            sqlConnectionObject = dbConnectorObject.GetConnection;

            try
            {
                sqlConnectionObject.Open();
                SqlCommand sqlCommandObject = new SqlCommand(sqlString, sqlConnectionObject);

                foreach (SqlParameter pr in parametersList)
                {
                    sqlCommandObject.Parameters.Add(pr);
                }

                int i = sqlCommandObject.ExecuteNonQuery();
                if (i > 0)
                    return true;
                else
                    return false;
            }

            catch (SqlException ex)
            {
                throw new Exception(" Database problem.\n" + ex.Message);
            }
            finally
            {
                if (sqlConnectionObject.State == System.Data.ConnectionState.Open)
                {
                    sqlConnectionObject.Close();
                }
            }
        }


        #endregion
    }
}

Selection:

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

namespace ShareLibrary.DAL.Gateways
{
   public class DataSelection
    {
        #region Member variables

        private DBConnector dbConnectorObject;
        private DataTable dataTableObject;
        private SqlConnection sqlConnectionObject;
        private SqlDataAdapter sqlDataAdepterObject;
        private DataSet dataSetObject;
      
        #endregion

       ///

       /// Return selected data
       ///

       ///
selection sql query
       ///
       public DataTable GetQueryResult(string selectingString)
       {
           dbConnectorObject = new DBConnector();
           dataTableObject = new DataTable();
           sqlConnectionObject = new SqlConnection();
           dataSetObject = new DataSet();
           try
           {
               sqlConnectionObject = dbConnectorObject.GetConnection;
               sqlDataAdepterObject = new SqlDataAdapter(selectingString, sqlConnectionObject);

               sqlDataAdepterObject.Fill(dataSetObject);

               dataTableObject = dataSetObject.Tables[0];

               if (dataSetObject.Tables[0].Rows.Count == 0)
               {
                   return null;
               }

               else
               {
                   return dataTableObject;
               }
           }

           catch (Exception ex)
           {
               throw new Exception("DataBase Problem." + ex.Message);
           }

           finally
           {
               if (sqlConnectionObject.State == ConnectionState.Open)
               {
                   sqlConnectionObject.Close();
               }
           }

       }
    }
}




///

        /// serialize the object to xml string and return it
        ///

        /// type of object to serialize
        ///
the object to serialize
        ///
        public static String ObjectToXml(ref T xmlObject)
        {
            using (StringWriter s = new StringWriter())
            {
                XmlSerializer xs = new XmlSerializer(typeof(T));

                xs.Serialize(s, xmlObject);
                return s.ToString();
            }
        }

        ///

        /// method to deserialize the xml data to the object type
        ///

        ///
        ///
        ///
        public static T XmlToObject(String xml)
        {
            string fixedString = xml;
            if (typeof(T) == typeof(DataTable))
            {
                string rp = @"(?\d{4}-\d{2}-\d{2})(?T\d{2}:\d{2}:\d{2}."
                            + @"\d{7}-)(?\d{2})(?:\d{2})";
                // Replace UTC offset value
                fixedString = Regex.Replace(xml, rp,
                        new MatchEvaluator(getHourOffset));

            }
            using (StringReader s = new StringReader(fixedString))
            {              
                XmlSerializer xs = new XmlSerializer(typeof(T));
                T temp = (T)xs.Deserialize(s);
                return temp;
            }
        }

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