VS Connect Sql--dbhelper

usingSystem;usingSystem.Collections.Generic;usingSystem.Data;usingSystem.Data.SqlClient;usingSystem.Text;usingSystem.Configuration;namespacedal{ Public classDBHelper {Private Static stringdbconnectstring = configurationmanager.connectionstrings["defaultconnection"].        ConnectionString; Private StaticSqlConnection Conn; Private StaticSqlDataAdapter da; Private StaticSqlCommand cmd; Private StaticDBHelper DBHelper;  PublicDBHelper () {conn=NewSqlConnection (dbconnectstring); }        /// <summary>        ///instantiating a DBHelper object/// </summary>        /// <returns></returns>         Public Staticdbhelper Instance () {if(DBHelper = =NULL) {DBHelper=NewDBHelper (); }            returnDBHelper; }        /// <summary>        ///Open a database connection/// </summary>        voiddbopen () {if(Conn. state = =connectionstate.closed) {conn.            Open (); }        }        /// <summary>        ///To close a database connection/// </summary>        voiddbclose () {if(Conn. state = =ConnectionState.Open) {conn.            Close (); }        }        /// <summary>        ///Execute SQL statement get DataSet/// </summary>        /// <param name= "SQL" >SQL statements</param>        /// <returns>DataTable Data Set</returns>         PublicDataTable Getdatatablebysql (stringSQL)            {dbopen (); DataTable DT=NewDataTable (); Da=NewSqlDataAdapter (SQL, conn); Try{da.                Fill (DT); returnDT; }            Catch            {                return NULL; }            finally{dbclose (); }        }        /// <summary>        ///Execute SQL statement/// </summary>        /// <param name= "SQL" >SQL statements</param>        /// <returns>whether the execution succeeds</returns>         Public BOOLExcutesql (stringSQL)            {dbopen (); CMD=NewSqlCommand (SQL, conn); Try{cmd.                ExecuteNonQuery (); return true; }            Catch            {                return false; }            finally{dbclose (); }        }        /// <summary>        ///Executing stored procedures/// </summary>        /// <param name= "Proname" >Stored Procedure name</param>        /// <param Name= "Paras" >Stored Procedure Parameters</param>        /// <returns>whether the execution succeeds</returns>         Public BOOLExcuteprocedure (stringProname, Sqlparameter[] paras)            {dbopen (); CMD=NewSqlCommand (PRONAME, conn); Cmd.commandtype=CommandType.StoredProcedure;  for(inti =0; I < paras. Length; i++) {cmd.            Parameters.Add (Paras[i]); }            Try{cmd.                ExecuteNonQuery (); return true; }            Catch            {                return false; }            finally{dbclose (); }        }        /// <summary>        ///executing a stored procedure to get a dataset/// </summary>        /// <param name= "Proname" >Stored Procedure name</param>        /// <param Name= "Paras" >Stored Procedure Parameters</param>        /// <returns>DataTable Data Set</returns>         PublicDataTable Getdatatablebyprocedure (stringProname, Sqlparameter[] paras)            {dbopen (); CMD=NewSqlCommand (PRONAME, conn); Cmd.commandtype=CommandType.StoredProcedure; Da=NewSqlDataAdapter (CMD); DataTable DT=NewDataTable ();  for(inti =0; I < paras. Length; i++) {cmd.            Parameters.Add (Paras[i]); }            Try{da.                Fill (DT); returnDT; }            Catch            {                return NULL; }            finally{dbclose (); }        }    }}

VS Connect Sql--dbhelper