如何从具有未来日期的变量中减去1个月？ [英] How do I subtract 1 month from my variable that has a future date?

问题描述

我想要做的是使用SQL获取上个月的报告。因此，如果查询今天（2018年5月7日）运行，我应该得到上个月的报告，即从4月1日到4月30日。

在我的vb.net代码中查询看起来像这样strSQL = GetSql （dtmStartDateTime，dtmEndDateTime）。

对于测试，我使用的是strALTCURDATE字符串变量中的未来日期（06/01/2018）。

如何将此变量用作dtmStartDateTime，然后从中减去1个月并将其用作dtmEndDateTime？

我还需要将strALTCURDATE转换为日期。

所以dtmStartDateTime应该是dtmStartDateTime = strALTCURDATE而dtmEndDateTime应该是dtmStartDateTime - 1月份是5月31日。

有人可以帮我吗？



我的dtmEndDateTime显示为5/6/2018，但我希望它显示为5/31/2018。



我尝试了什么：



我试过了

dtmStartDateTime = DateTime.Parse（strALTCURDATE）

dtmEndDateTime = DateTime（AddInterval.Month，-1，dtmStartDateTime）

strSQL = GetSql（dtmStartDateTime，dtmEndDateTime）

What I am trying to do is using SQL get last month's report. So if the query runs today (May 07 2018), I should get a report for last month i.e. from April 1 to April 30.
In my vb.net code the query looks like this strSQL = GetSql(dtmStartDateTime, dtmEndDateTime).
For testing I am using a future date (06/01/2018) which is in strALTCURDATE string variable.
How do I use this variable as dtmStartDateTime and then subtract 1 month from it and use that as dtmEndDateTime?
I also need to convert strALTCURDATE to a date.
So dtmStartDateTime should be dtmStartDateTime = strALTCURDATE and dtmEndDateTime should be dtmStartDateTime - 1 month which is May 31.
Can someone help me with this please?

My dtmEndDateTime is showing as 5/6/2018 but I would like it to show as 5/31/2018.

What I have tried:

I have tried
dtmStartDateTime = DateTime.Parse(strALTCURDATE)
dtmEndDateTime = DateTime(AddInterval.Month, -1, dtmStartDateTime)
strSQL = GetSql(dtmStartDateTime, dtmEndDateTime)

推荐答案

检查这个：

Check this:

Dim tdate As DateTime = DateTime.Today
Dim sdate As DateTime = New DateTime(tdate.Year, tdate.Month-1, 1)
Dim edate As DateTime = sdate.AddMonths(1).AddDays(-1)


Console.WriteLine("Today is: '{0}'", tdate.ToString("yyyy-MM-dd"))
Console.WriteLine("Report date range is: '{0}' and '{1}'", sdate.ToString("yyyy-MM-dd"), edate.ToString("yyyy-MM-dd"))

结果：

Result:

Today is: '2018-05-07'
Report date range is: '2018-04-01' and '2018-04-30'

你可以这样做：

You could do it like this:

Dim curDateTime = DateTime.Parse(strALTCURDATE)
Dim prevMonth = curDateTime.AddMonths(-1)

Dim firstOfPrevMonth = New Date(prevMonth.Year, prevMonth.Month, 1)
Dim firstOfCurMonth = New Date(curDateTime.Year, curDateTime.Month, 1)
Dim lastOfPrevMonth = firstOfCurMonth.AddDays(-1)

firstOfPrevMonth将是您的开始日期，lastOfPrevMonth将是您的结束日期。

"firstOfPrevMonth" will be your start date and "lastOfPrevMonth" your end date.

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