关于asp.net：最佳实践：LINQ To SQL进行数据访问

protected void MessageListDataSource_Selecting(object sender, LinqDataSourceSelectEventArgs e)
{
    var db = new DataContext();

    // parse the input strings from the web form
    int categoryIDFilter;
    DateTime dateFilter;
    string catFilterString = MessagesCategoryFilter.SelectedValue;
    string dateFilterString = MessagesDateFilter.SelectedValue;
    // TryParse will return default values if parsing is unsuccessful (i.e. if"all" is selected"):
    // DateTime.MinValue for dates, 0 for int
    DateTime.TryParse(dateFilterString, out dateFilter);
    Int32.TryParse(catFilterString, out categoryIDFilter);
    bool showRead = MessagesReadFilter.Checked;

    var messages =
        from detail in db.MessageDetails
        where detail.UserID == (int)Session["UserID"]
        where detail.Message.IsPublished
        where detail.Message.MessageCategoryID == categoryIDFilter || (categoryIDFilter == 0)
        where dateFilter == detail.Message.PublishDate.Value.Date || (dateFilter == DateTime.MinValue)
        // is unread, showRead filter is on, or message was marked read today
        where detail.IsRead == false || showRead || detail.ReadDate.Value.Date == DateTime.Today
        orderby detail.Message.PublishDate descending
        group detail by detail.Message.MessageCategory into categories
        orderby categories.Key.Name
        select new
        {
            MessageCategory = categories.Key,
            MessageDetails = categories.Select(d => d)
        };

    e.Result = messages;
}