LINQ to Entities group by by failure using .date [英] LINQ to Entities group-by failure using .date

问题描述

这个linq语句的工作原理是按日期和时间进行分组。

  var myQuery = from p in dbContext.Trends 
 group p by p.UpdateDateTime into g 
选择新的{k = g.Key，ud = g.Max（p => p.Amount）}; 
  

当我运行这个语句来分组，只是日期我得到以下错误

  var myQuery = from p in dbContext.Trends 
 group p by p.UpdateDateTime.Date into g //在此行添加了.Date 
 select new {k = g.Key，ud = g.Max（p => p.Amount）}; 
  

LINQ to Entities不支持指定的类型成员'Date'。
仅支持初始值设定，实体成员和实体导航属性。

如何在日期进行组，而不是日期和时间？ / p>

解决方案

使用 EntityFunctions.TruncateTime 方法：

  var myQuery = from p in dbContext.Trends 
组p由EntityFunctions.TruncateTime（p.UpdateDateTime）转换为g 
 select new {k = g.Key，ud = g.Max（p => p.Amount）}; 
  

I am trying to do a Linq group by on just the date part of a datetime field.

This linq statement works but it groups by the date and the time.

var myQuery = from p in dbContext.Trends
          group p by p.UpdateDateTime into g
          select new { k = g.Key, ud = g.Max(p => p.Amount) };

When I run this statement to group by just the date I get the following error

var myQuery = from p in dbContext.Trends
          group p by p.UpdateDateTime.Date into g   //Added .Date on this line
          select new { k = g.Key, ud = g.Max(p => p.Amount) };

The specified type member 'Date' is not supported in LINQ to Entities. Only initializers, entity members, and entity navigation properties are supported.

How can I do a group by for the date and not the date and time?

解决方案

Use the EntityFunctions.TruncateTime method:

var myQuery = from p in dbContext.Trends
          group p by EntityFunctions.TruncateTime(p.UpdateDateTime) into g
          select new { k = g.Key, ud = g.Max(p => p.Amount) };

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