在C＃搜索linq的日期 [英] Search dates in linq in C#

问题描述

我有员工工资修改历史



并且需要查找搜索期间的工资是什么



薪水在以下日期被修改



08/03/2017它是2200美元，变成2300

24 / 12/2018它是2300 US并且变成了2400

25/12/2018它是2400美元并且变成2300

17/02/2019它是2300美国并且变成了2400





如果我在 26/01/2017至2017年2月25日期间搜索工资如果我在 26/02/2017至2017年3月25日期间搜索工资，我预计结果为2200



如果我在 26/11/2018至2017年12月25日期间搜索工资，我预计结果为2300



如果我在 26/12/2018至25/01/2019期间搜索工资，我预计结果为2400










我的c＃代码的问题是它从2017年3月8日到2017年2月17日返回整个日期


在上述搜索时段的任何时段




i需要上述预期结果我能做些什么来获得正确的结果







我尝试过：

i have employee salary modification history

and need to find what is the salary for the searched period for example

salary have been modified in the following dates

08/03/2017 it was 2200 US and became 2300
24/12/2018 it was 2300 US and became 2400
25/12/2018 it was 2400 US and became 2300
17/02/2019 it was 2300 US and became 2400


if i searched for salary at the period from 26/01/2017 to 25/02/2017 i expect the result to be 2200

if i searched for salary at the period from 26/02/2017 to 25/03/2017 i expect the result to be 2300

if i searched for salary at the period from 26/11/2018 to 25/12/2017 i expect the result to be 2400

if i searched for salary at the period from 26/12/2018 to 25/01/2019 i expect the result to be 2300



the problem with my c# code that it return the whole dates from 08/03/2017 to 17/02/2019

at any period from the searched periods above

i need the above expected results what can i do to obtain correct result



What I have tried:

var dbitem = db.tblSalaryHistories.Where(c => c.Employee_ID == employeeId && (
                         (startDate <= c.Update_Date && endDate >= c.Update_Date) ||
                         (startDate >= c.Update_Date && endDate <= c.Update_Date) ||
                         (startDate <= c.Update_Date) ))

推荐答案

问题是你的代码完全符合你的要求：返回所有数据。

这是因为你有OR条件相当于：

The problem is that your code does exactly what you ask of it: returns all data.
This is because you have OR conditions which amount to:

(a <= b && c >= b) || (a >= b && c <= b) || (a <= b)

因此，如果在任何时候，a< b，整个条件都是真的。第一个条件是无关紧要的，因为第三个条件在第一个条件时始终为真。



因此，如果您搜索26-01-2017的startDate，if会自动匹配样本数据中的所有行，并返回它们。



如果您提供订单 - 也许是通过c.UpdateDate升序，您可以使用FirstOrDefault而不是Where返回单行，但即便如此，我认为您希望看得更接近在您的情况下，可能会将其减少到

So, if at any time, a < b, the whole condition is true. The first condition is irrelevant because the third will always be true when the first is.

So if you search for a startDate of 26-01-2017, if will automatically match all rows in your sample data, and return them.

If you provide an order - perhaps by c.UpdateDate ascending, you could use FirstOrDefault instead of Where to return a single row, but even then, I think you want to look rather more closely at your condition and probably reduce it to

startDate <= c.Update_Date && endDate >= c.Update_Date

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