计算不同行上两个日期之间的时间间隔

鉴于SQL没有任何聚合差异方法,我建议将表连接到自身,并从连接的每一侧选择您要查找的每一行。

var diff = from a in db.Events
           join b in db.Events on a.SessionId equals b.SessionId
           where a.EventType == 'Login' && b.EventType == 'Logout'
           select b.EventTime - a.EventTime;

编辑:更新以适应新提供的信息。

var query = from a in (from log in data.Elements()
                       select new {
                          date = DateTime.Parse(log.Element("DateTime").Value),
                          msg = log.Element("MessageText").Value
                       })
            select new {
                a.date,
                type = a.msg.Contains("login") ? "Login" : "Logout",
                user = a.msg.Substring(a.msg.LastIndexOf(',') + 1)
            };

var results = from a in query
            join b in query on a.user equals b.user
            where a.type == "Login" && b.type == "Logout"
                && b.date == (query.OrderBy(o => o.date).Where(d => d.date > a.date).FirstOrDefault().date)
            select new {
                a.user,
                Login = a.date,
                Logout = b.date             
            };