<connectionStrings>
　　<add name="dh_web" connectionString="Data Source=xxx.com;Initial Catalog=xx_db;User ID=xx;Password=**;
　　　　　　pooling=true;max pool size=200" providerName="System.Data.SqlClient"/>
</connectionStrings>

public class DBHelper
    {
        private static string connectionString = ConfigurationManager.ConnectionStrings["dh_web"].ConnectionString;
      
        //不帶參數的執行命令
        public static int ExecuteCommand(string safeSql)
        {
            using (SqlConnection connection = new SqlConnection(connectionString))
            {
                connection.Open();
                SqlCommand cmd = new SqlCommand(safeSql, connection);
                return cmd.ExecuteNonQuery();
            }
        }
        //帶參數的執行命令
        public static int ExecuteCommand(string sql, params SqlParameter[] values)
                SqlCommand cmd = new SqlCommand(sql, connection);
                cmd.Parameters.AddRange(values);
 
        public static int GetScalar(string safeSql)
                return Convert.ToInt32(cmd.ExecuteScalar());
        public static int GetScalar(string sql, params SqlParameter[] values)
        public static SqlDataReader GetReader(string safeSql)
            SqlConnection connection = new SqlConnection(connectionString);
            connection.Open();
            SqlCommand cmd = new SqlCommand(safeSql, connection);
            return cmd.ExecuteReader(CommandBehavior.CloseConnection);
        public static SqlDataReader GetReader(string sql, params SqlParameter[] values)
            SqlCommand cmd = new SqlCommand(sql, connection);
            cmd.Parameters.AddRange(values);
        public static DataTable GetDataSet(string safeSql)
                DataSet ds = new DataSet();
                SqlDataAdapter da = new SqlDataAdapter(cmd);
                da.Fill(ds);
                return ds.Tables[0];
        public static DataTable GetDataSet(string sql, params SqlParameter[] values)
            {               
    }