在linq和EF中按月排序 [英] Sort by month in linq and EF

问题描述

我有一个linq查询，它的内部是月份名称.我希望结果按月份(1月，2月，3月，...)排序.

I have a linq query and inside of it is the month name. I want the results sorted by the month (Jan, Feb, Mar, ...).

目前，我有以下内容，但它给了我错误:

Currently I have the below but it's giving me and error:

LINQ to Entities无法识别方法'System.DateTime Parse(System.String)'方法，并且此方法无法转换 进入商店表达式.

LINQ to Entities does not recognize the method 'System.DateTime Parse(System.String)' method, and this method cannot be translated into a store expression.

var shockValues = (from s in ctx.Shocks
                               where s.ID == id
                               orderby DateTime.Parse(s.MonthName)
                               select new 
                               {
                                   val = s.MonthName + "=" + s.ShockValue
                               });

推荐答案

您别无选择.您可以使用一长串可选的运算符将名称映射到数字

You've got few options. You could use a long list of optional operators to map the names to numbers

order by s.MonthName == "Jan" ? 1 : s.MonthName == "Feb" ? 2 : ...

您可以在数据库中创建一个表，将名称映射到数字值

You could create a table in your DB that maps the names to nummeric values

var shockValues = (from s in ctx.Shocks
                   join o in MonthOrder on s.MonthName equals o.MonthName
                   where s.ID == id
                   orderby o.MonthNumber
                   select new 
                   {
                       val = s.MonthName + "=" + s.ShockValue
                   });

或者在内存中进行排序

var shockValues = (from s in ctx.Shocks
                   where s.ID == id
                   select new
                          {
                              s.MonthName,
                              s.ShockValue
                          })
                  .AsEnumerable()
                  .OrderBy(s => DateTime.ParseExact(s.MonthName, "MMM", CultureInfo.InvariantCulture).Month)
                  .Select(s => new 
                               {
                                   val = s.MonthName + "=" + s.ShockValue
                               });

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