sqlHelper+app.config

public class SqlHelper
    {
        /// <summary>
        /// 获取连接字符串
        /// </summary>
        public static string ConString = ConfigurationManager.ConnectionStrings["HotelManagerConnectionString"].ToString();
        public static string Dbowner = ConfigurationManager.ConnectionStrings["DataBaseOwner"].ToString();

        ///  <Summary> 
        /// disposed performing tool
         ///  </ Summary> 
        ///  <param name = "CON"> connection object </ param> 
        ///  <param name = "cmd"> tool </ param> 
        ///  <param name = "Paras"> parameter array </ param> 
        ///  <param name = "sqlstr"> the SQL statement </ param> 
        ///  <param name = "cmdType"> command type < / param> 
        public  static  void PrepareCommand (the SqlConnection CON, the SqlCommand cmd, the SqlParameter [] Paras, String sqlstr, the CommandType cmdType)
        {
            if(con.State != ConnectionState.Open)
            {
                con.Open();
            }
            cmd.Connection = con;
            cmd.CommandType = cmdType;
            cmd.CommandText = sqlStr;
            if(paras==null)
            {
                return;
            }
            else
            {
                foreach (SqlParameter p in paras)
                {
                    cmd.Parameters.Add(p);
                }
            }
        }

        /// <summary>
        /// 执行查询，返回数据集
        /// </summary>
        /// <param name="cmdType"></param>
        /// <param name="cmdText"></param>
        /// <param name="commandPrarmeters"></param>
        /// <returns></returns>
        public static DataTable Execute(CommandType cmdType, string cmdText, params SqlParameter[] commandPrarmeters)
        {
            SqlConnection connection = new SqlConnection(ConString);
            SqlCommand cmd = new SqlCommand();
            PrepareCommand(connection, cmd, commandPrarmeters, cmdText, cmdType);
            SqlDataAdapter dap = new SqlDataAdapter(cmd);
            DataSet ds = new DataSet();
            dap.Fill(ds);
            return ds.Tables[0];
        }

        /// <summary>
        /// 查询首行首列的值
        /// </summary>
        /// <param name="cmdType"></param>
        /// <param name="cmdText"></param>
        /// <param name="commandPrarmeters"></param>
        /// <returns></returns>
        public static object ExecuteScalar(CommandType cmdType,string cmdText, params SqlParameter[] commandPrarmeters)
        {
            SqlCommand cmd = new SqlCommand();
            using (SqlConnection connection = new SqlConnection (ConString))
            {
                PrepareCommand(connection, cmd, commandPrarmeters, cmdText, cmdType );
                Object Val cmd.ExecuteScalar = (); // returns first row and first column of the query 
                return Val;
            }
        }

        /// <summary>
        /// 获取reader对象
        /// </summary>
        /// <param name="cmdText"></param>
        /// <param name="cmdType"></param>
        /// <param name="commandParameters"></param>
        /// <returns></returns>
        public static SqlDataReader GetDataReader(string cmdText, CommandType cmdType, params SqlParameter[] commandParameters)
        {
            SqlCommand cmd = new SqlCommand();
            SqlConnection conn = new SqlConnection(ConString);
            try
            {
                PrepareCommand(conn, cmd, commandParameters, cmdText, cmdType);
                // SqlDataReader must open the database to run, so use commandBehavior overloaded, while closing the Connection 
                SqlDataReader RDR = cmd.ExecuteReader (CommandBehavior.CloseConnection);
                cmd.Parameters.Clear();
                return rdr;
            }
            catch(Exception)
            {
                conn.Close();
                throw;
            }
        }

        /// <summary>
        /// 执行增删改，返回受影响行数
        /// </summary>
        /// <param name="cmdText"></param>
        /// <param name="cmdType"></param>
        /// <param name="commandParameters"></param>
        /// <returns></returns>
        public static int ExecuteNonQuery(string cmdText, CommandType cmdType, params SqlParameter[] commandParameters)
        {
            SqlCommand cmd = new SqlCommand();
            using (SqlConnection conn = new SqlConnection (ConString))
            {
                PrepareCommand(conn, cmd, commandParameters , cmdText, cmdType);
                int val = cmd.ExecuteNonQuery();
                return val;
            }
        }
    }

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <connectionStrings >
    <add name="DataBaseOwner"  connectionString="dbo"/>
    <add name ="HotelManagerConnectionString" connectionString="Data Source=.;Database=HotelManageEx;User ID=sa;Password=123" providerName ="System.Data.SqlClient"/>
  </connectionStrings>
  <appSettings>
    <add key="DBtype" value="Sql"/>
  </appSettings>
    <startup> 
        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5.2" />
    </startup>
</configuration>