Linq to SQL/过滤重复项 [英] Linq to SQL / filter duplicates

问题描述

我在我的 sql server 2012 中有一个视图，有几个重复项，我想按最新对它们进行排序并过滤所有其他视图 - 谁能帮我?

i have a view in my sql server 2012 with a couple of duplicates and i want to sort them by the newest and filter all others - can anyone help me?

我在 SQL Server 2012 中的视图:

My viewin my SQL Server 2012:

GUID(作为主键)、数字、日期时间和名称

GUID (as primary key), number, datetime and name

+-----+----------+--------------------------------+-----
| guid  |  number| datetime                       | name
+-----+----------+--------------------------------+------
| b105..| 1234567|2014-07-07T16:32:20.854+02:00:00|Name1
| s1b5..| 1111222|2014-07-06T16:30:21.854+02:00:00|Name2
| b17a..| 1234567|2014-07-06T15:22:17.854+02:00:00|Name1
| f205..| 1233333|2014-07-07T17:40:20.854+02:00:00|Name3
| b11t..| 1233333|2014-07-04T11:12:15.854+02:00:00|Name3
| rt85..| 1111222|2014-07-07T21:55:52.854+02:00:00|Name2
+-------+--------+--------------------------------+-----

如果号码相同，则名称每次都相同.例如编号 1234567 始终是名称 1.

the name is every time the same if the number is the same. for e.g. number 1234567 is always name 1.

我想过滤我的表格，我只有最新的数字没有重复

I want to filter my table that i have only the newest number without duplicates

所以结果应该是:

+-----+----------+--------------------------------+-----
| guid  |  number| datetime                       | name
+-----+----------+--------------------------------+------
| b105..| 1234567|2014-07-07T16:32:20.854+02:00:00|Name1
| f205..| 1233333|2014-07-07T17:40:20.854+02:00:00|Name3
| rt85..| 1111222|2014-07-07T21:55:52.854+02:00:00|Name2
+-------+--------+--------------------------------+-----

我怎样才能在 Linq 中做到这一点?由于 guid 和日期时间，Distinct"不起作用

How can i do this in Linq? "Distinct" is not working because of the guid and the datetime

推荐答案

var res = list.GroupBy(c => c.name).Select(group => group.OrderBy( c1 => c1.datetime).First()).ToList();

只要 datetime 存储为 DateTime 的实例，而不是字符串，这应该可以工作.

This should work as long as datetime is stored as an instance of DateTime, instead of string.

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