foreach (PropertyInfo fi in typeof(Product).GetProperties())
            {
                if (fi.GetCustomAttributes(false).Length > 0&&fi.GetCustomAttributes(false)[0] is ColumnAttribute)
                {
                    ColumnAttribute c = fi.GetCustomAttributes(false)[0] as ColumnAttribute;
                    if (c.IsPrimaryKey)
                    {
                        string a = fi.Name;
                    }
                }
            }