VB.net 在预定时间执行任务 [英] VB.net Perform task at scheduled Time

问题描述

我需要使用用户输入的小时和分钟在特定时间执行任务.

i need to perform a task at a certain time using the using the user inputted Hour and Minute.

我正在考虑使用某种循环，每次循环时，检查 Now().Hour 是否匹配 HourChoice 和 Now().Minute 匹配 MinuteChoice

I'm thinking of something like using some sort of loop that every time it loops, checks if the Now().Hour matches HourChoice and the Now().Minute matches the MinuteChoice

在这里，我还有一个用户选项来选择AM"或PM"，如果 TimeOfDay = "PM"，添加 12 小时(Now().Hour 是军用时间).

In this, i also have a user option to chose "AM" or "PM", and if TimeOfDay = "PM", add 12 hours (The Now().Hour is military time).

我只希望它一次运行一次，而不是每天运行一次.

I only want this to run once at a time, not every day.

推荐答案

您可以使用 System.Threading.Timer 来做到这一点.您可以将 Timer 的时间间隔设置为现在和所选时间之间的差异，并将 TimerCallback 设置为 Sub 完成任务工作.将超时设置为 0 或 Timeout.Infinite 将确保只执行一次.

You could use a System.Threading.Timer to do this. Instead of a loop that constantly runs and sleeps, you could set the interval to the Timer to be the difference between now and the selected time and the TimerCallback to be the Sub that does the task work. Setting the timeout to 0 or Timeout.Infinite will make sure this is only executed once.

示例

Dim tcb As TimerCallback = AddressOf DoStuff
Dim t As Timer
Dim execTime As TimeSpan
Dim dtNow As DateTime = DateTime.Now
Dim hc As Integer = HourChoice
Dim mc As Integer = MinuteChoice

If TimeOfDay = "AM" And hc = 12 Then
    hc = 0
Else If TimeOfDay = "PM" Then
    hc = hc + 12
End If

Dim dtCandidate As DateTime = New DateTime(dtNow.Year, dtNow.Month, dtNow.Day, hc, mc, 0)

If dtCandidate < dtNow Then
    dtCandidate.AddDays(1)
End If

execTime = dtCandidate.Subtract(dtNow)
t = New Timer(tcb,Nothing,execTime,TimeSpan.Zero)

那么你只需要一个 Sub 来完成你的任务:

Then you just need a Sub to do your task:

Public Sub DoStuff(obj As Object)
'...Do Some Kind of Work
End Sub

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