LINQ到实体组的故障使用.date [英] LINQ to Entities group-by failure using .date

问题描述

我想通过只是时间字段的日期部分做一个LINQ组。

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

这LINQ声明的日期和时间的作品，但它组。

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) };

当我刚好我得到以下错误的日期运行此语句组

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) };

指定类型的成员'日期'不是在LINQ支持实体。
只有初始化，实体成员和实体导航属性都支持。

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

我如何通过的日期，而不是​​日期和时间做一组？

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

推荐答案

使用 EntityFunctions.TruncateTime 方法：

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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