Linq 日期分组

from a in DB group a by  
new
{ 
   Date = a.OperDate.Date 
   //或Date = EntityFunctions.CreateDateTime(a.OperDate.Year,...) 
}

上面两种方式均会报错，请问该如何正确按日期分组？
[解决办法]

var list=DB.Select(t => { return new { OperDate = t.OperDate.ToString("yyyy-MM-dd") }; }).ToList();  
list = list.GroupBy(g=>g.OperDate).Select(t => { return new { OperDate = t.Key, count = t.Count() }; });

[解决办法]
from a in DB group a by a.OperDate.Date
or
from a in DB group a by a.OperDate.Date.Year * 32 * 12 + a.OperDate.Date.Month * 32 + a.OperDate.Date.Day
[解决办法]

from a in DB 
group a by EntityFunctions.TruncateTime(a.OperDate) into g
select g.Key  

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比如LINQ provider类型，报错异常信息，出错代码段 以及你做过的尝试等等~~