Question

我有一个类列表，其中包含事件名称，时间戳和持续时间（时间跨度）。有许多重复的事件名称。我想通过事件名称对它们进行合并，并添加它们的持续时间并保留最早的时间戳，除非事件具有某个名称。即，删除重复的事件名称，添加类似事件名称的持续时间，并保留偶数名称的最早时间戳。

有更好的方法吗？可能还有Linq？

这是我尝试过的，似乎没有正确合并（仍然有重复但却少了）

班级：

public class eventRecords
{
    public DateTime TimeStamp { get; set; }
    public string Event { get; set; }
    public TimeSpan Duration { get; set; }
}

我的尝试：

// allEventList is already sorted by TimeStamp, so my thinking is adding
// the first occurrence of an event to newList will keep the earliest
// TimeStamp in eventRecrods for that event
// Also - the duplicates are almost all consecutive in allEventList

var newList = new List<eventRecords>();
for (int ii = 0; ii < allEventList.Count; ii++ )
{
    newList.Add(allEventList[ii]);
    if((ii + 1) < allEventList.Count && allEventList[ii] != keyword)
    {
        if(allEventList[ii].Event == allEventList[ii+1].Event)
        {
            newList.Last().Duration = newList.Last().Duration+ allEventList[ii + 1].Duration; 
            ii = ii + 1;
        }

    }

}

例如，如果allEventList包含：

Event = "Action 1", TimeStamp = 08:00, Duration = TimeSpan.FromMinutes(1);
Event = "Action 1", TimeStamp = 09:00, Duration = TimeSpan.FromMinutes(1);
Event = "Action 1", TimeStamp = 10:00, Duration = TimeSpan.FromMinutes(1);
Event = "KeyWord", TimeStamp = 11:00, Duration = TimeSpan.FromMinutes(1);
Event = "Action 2", TimeStamp = 12:00, Duration = TimeSpan.FromMinutes(1);
Event = "Action 2", TimeStamp = 13:00, Duration = TimeSpan.FromMinutes(1);

newList应包含：

Event = "Action 1", TimeStamp = 08:00, Duration = TimeSpan.FromMinutes(3);
Event = "KeyWord", TimeStamp = 11:00, Duration = TimeSpan.FromMinutes(1);
Event = "Action 2", TimeStamp = 12:00, Duration = TimeSpan.FromMinutes(2);

Answer 1

这一点相当容易

我想按事件名称合并它们并添加其持续时间并保留最早的时间戳

allEventList.GroupBy(e => e.Event)
        .Select(g => new eventRecords{
             TimeStamp = g.Min(e => e.TimeStamp),
             Event = g.Key,
             Duration = new TimeSpan(g.Sum(e => e.Duration.Ticks))
         });

这首先按Event对您的列表进行分组，然后为您提供IEnumerable<IGrouping<string,eventRecords>>。然后使用Select投影这些群组以构建新的eventRecords，并根据要求汇总所需的素材。

实例：http://rextester.com/MTVNH46675

在回答您的评论时，您可以在使用Where对其进行分组之前对列表进行过滤。例如，如果您只想要事件名称长度大于5的事件（设想示例！）

allEventList.Where(e => e.Event.Length>5)
            .GroupBy(e => e.Event)
            .... etc

Answer 2

怎么样：

allEventList
    .GroupBy(x => x.Event)
    .Select(grouping => new eventRecords
                {
                    Event = grouping.Key,
                    TimeStamp = grouping.Min(entry => entry.TimeStamp),
                    Duration = new TimeSpan(grouping.Sum(entry => entry.Duration.Ticks))
                };

可能grouping.Min(entry => entry.TimeStamp)可以替换为grouping.First().TimeStamp。我不知道GroupBy是否保留了订单。

Answer 3

我认为这就是你所追求的：

 var list = new List<EventRecords>();

 list.Add(new EventRecords{ TimeStamp = new DateTime(2014,1,1), Event = "1", Duration = new TimeSpan(1)});
 list.Add(new EventRecords { TimeStamp = new DateTime(2013, 1, 1), Event = "1", Duration = new TimeSpan(1) }); 
 list.Add(new EventRecords { TimeStamp = new DateTime(2014, 1, 1), Event = "2", Duration = new TimeSpan(1) });
 list.Add(new EventRecords { TimeStamp = new DateTime(2012, 1, 1), Event = "3", Duration = new TimeSpan(1) });

 var output = list.GroupBy(e => e.Event)
            .Select(e => new EventRecords
            {
                Event = e.Key,
                Duration = new TimeSpan(e.Sum(ee => ee.Duration.Ticks)),
                TimeStamp = e.Select(ee => ee.TimeStamp).Min()
            });

对于具有相同事件名称的项目，请将它们的时间长度相加：

new TimeSpan(e.Sum(ee => ee.Duration.Ticks)),
//create a new timespan from the sum of all timespan ticks

并抓住他们最早的时间戳：

e.Select(ee => ee.TimeStamp).Min()

只有一个条目的项目将保持不变

Answer 4

我使用了Northwind数据库，但这似乎可以做你想要的：

from o in Orders
where o.CustomerID != "HANAR"
group o by o.CustomerID into ox
select new 
{
    Event = ox.Key,
    Start = ox.Min (o => o.OrderDate),
    Duration = ox.Sum(o=>o.Freight)
}

合并单个类列表

4 个答案: