我这里有同样的问题贴： LINQ使用.date

然而，得到的答案是不是100％正确。它的工作原理在所有情况下，除非不同的时区的使用。当不同的时区时，它也对基时区。为什么？ 我设法通过多种实体的职能绕过这一点。

  INT localOffset = Convert.ToInt32（
    TimeZone.CurrentTimeZone.GetUtcOffset（DateTime.Now）.TotalMinutes）;

VAR的结果=（
    从perfEntry在db.entry
    哪里 （....）
    选择新{
        perfEntry.Operation，perfEntry.Duration，
        本地时间= EntityFunctions.AddMinutes（perfEntry.Start，
            localOffset  -  EntityFunctions.GetTotalOffsetMinutes（
                perfEntry.Start））
    }
）.GroupBy（X =＆gt;新建{
    时间= EntityFunctions.TruncateTime（
        EntityFunctions.CreateDateTime（x.localTime.Value.Year，
            x.localTime.Value.Month，x.localTime.Value.Day，0，0，0）），
    x.Operation}
）.OrderByDescending（一个=＆GT; a.Key）。
选择（G =＆gt;新建{
    时间= g.Key.Time，
    ...
}）;
 

有没有人在那里谁知道如何做到这一点的正确方法？这code是那么难看，可能效率非常低。

更新（警告）： 我也意识到了功能EntityFunctions.CreateDateTime从错误受到影响。它不兼容闰年，比如今年。 2012年2月29日将抛出异常。

您可以使用UTC日期时间和之后trunkate的时间。

I have the same problem posted here: LINQ to Entities group-by failure using .date

However, the answer is not 100% correct. It works in all cases except when different timezones are used. When different timezones are used, it also groups on timezones. Why? I managed to bypass this by using many entity functions.

int localOffset= Convert.ToInt32(
    TimeZone.CurrentTimeZone.GetUtcOffset(DateTime.Now).TotalMinutes);

var results = (
    from perfEntry in db.entry
    where (....)
    select new { 
        perfEntry.Operation, perfEntry.Duration, 
        localTime = EntityFunctions.AddMinutes(perfEntry.Start, 
            localOffset - EntityFunctions.GetTotalOffsetMinutes(
                perfEntry.Start)) 
    }
).GroupBy(x => new { 
    Time = EntityFunctions.TruncateTime(
        EntityFunctions.CreateDateTime(x.localTime.Value.Year,
            x.localTime.Value.Month, x.localTime.Value.Day, 0, 0, 0)),
    x.Operation }
).OrderByDescending(a => a.Key).
Select(g => new {
    Time = g.Key.Time,
    ...
});

Is there someone out there who knows how to do this the proper way? This code is so ugly and probably very inefficient.

UPDATE (warning): I also realised that the function EntityFunctions.CreateDateTime suffers from a bug. Its not compatible with leap years, such as this year. 29 feb 2012 will throw an exception.

You can use UTC DateTime and trunkate the time after it.