VB.net Run code at certain time today


If I have the time in a string (eg 11:00), and I turn my computer on I want to set a timer to run certain code on that hour.
What VB.net code do I use to do this?
Murray BrownMicrosoft Cloud Azure/Excel Solution DeveloperAsked:
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Russ SuterSenior Software DeveloperCommented:
You have two options that I can think of.

1. Create a simple console application and run it as a scheduled task.
2. Create a Windows service application and include logic that executes the code at a scheduled interval.

The first is much easier to implement but relies on the Windows Task Scheduler. The second takes quite a bit more setup but has no external dependencies. There are many articles explaining how to create a service. A couple of the better ones are:


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Mike TomlinsonHigh School Computer Science, Computer Applications, and Mathematics TeachersCommented:
Assuming you set your VB.Net application to be run at startup somehow (and you plan on leaving it RUNNING, whether visible or not until the desired time), you'd simply parse the time and setup a DateTime variable to hold your target date/time (be it today if that time has not occurred yet, or tomorrow at that time if we are already past the desired time of day).

Once you've got your target DateTime you have two basic options:
(1) Poll the current date/time to see if we are past the target date/time
(2) Calculate the duration of time to the target date/time and put some kind of thread to "sleep" for that amount of time.

An example of (1), which is useful, for example, if you need to display some kind of progress towards the target time or a countdown:
Public Class Form1

    Private targetTime As DateTime
    Private scheduledTime As String = "11:00"
    Private WithEvents Tmr As New System.Windows.Forms.Timer

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        Tmr.Interval = 1000
        Tmr.Enabled = False
    End Sub

    Private Sub SetTarget()
        ' allow various time formats and attempt to parse the scheduled time: (with or without leading zeroes, allow am/pm or 24 hour format)
        Dim allowed() As String = {"h:mm", "hh:mm", "h:mm tt", "hh:mm tt", "H:mm", "HH:mm"}
        If DateTime.TryParseExact(scheduledTime, allowed, Nothing, Globalization.DateTimeStyles.None, targetTime) Then
            If targetTime < DateTime.Now Then
                ' we're already past the target time, schedule it for tomorrow at the same time:
                targetTime = targetTime.AddDays(1)
            End If
        End If
    End Sub

    Private Sub Tmr_Tick(sender As Object, e As EventArgs) Handles Tmr.Tick
        Dim ts As TimeSpan = targetTime.Subtract(DateTime.Now)
        If ts.TotalMilliseconds <= 0 Then
            MessageBox.Show("Target Time Reached!")

            ' set it up again?
            ' display time remaining?
            Label1.Text = "Alarm Time: " & scheduledTime
            Label2.Text = "Current Date/Time: " & DateTime.Now
            Label3.Text = "Time Remaining: -" & ts.ToString("hh\:mm\:ss")
        End If
    End Sub

End Class

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Polling for a Target Time
Murray BrownMicrosoft Cloud Azure/Excel Solution DeveloperAuthor Commented:
Thanks very much
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Visual Basic.NET

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