Groupby 方法语法

对序列进行分类汇总，汇总后产生的序列的key就是按照某个字段汇总的项 。groupby select Viewmodel三者常一起使用，用于统计。groupby 方法语法常与select  子句形成数据 viewModel 的 数据投影。public ActionResult Index()
{
    var context = new SiteDataContext();

    var notifications = context.Notifications
        .GroupBy(n => n.NotificationType)
        .Select(g => new NotificationViewModel
        {
            Count = g.Count(),
            NotificationType = g.Key.ToString(),
            BadgeClass = NotificationType.Email == g.Key
                ? "success"
                : "info"
        });

    ViewBag.Notifications = notifications;

    return View();
}