Looking for More Efficient Code

Question

Looking for More Efficient Code

RogerSchlueter-7899 1,801

Here is the code I've written to implement a count down timer.

A TextBox displays the time remaining in hours, minutes and seconds. The variable StartPeriod defines the starting time of the timer.

First I set up the timer:

Private Sub StartClock(sender As Object, e As RoutedEventArgs) Handles btnStart.Click
	tmr = New Timer(1000) With {.AutoReset = True, .Enabled = True}
	AddHandler tmr.Elapsed, AddressOf UpdateClock
	<< Code to set StartPeriod >>.
End Sub

Then I use this subroutine to initiate the clock update:

Private Sub UpdateClock(source As Object, e As ElapsedEventArgs)
	Dispatcher.Invoke(Sub() PopulateTimer())
End Sub

Finally, this is the subroutine that actually does the updating:

Private Sub PopulateTimer()
	If StartPeriod > 0 Then
		StartPeriod -= 1
		Dim HourCount As String = (CInt(StartPeriod) \ (60 * 60)).ToString("00:")
		Dim Remainder As Integer = CInt(StartPeriod) Mod (60 * 60)
		Dim MinuteCount As String = (Remainder \ 60).ToString("00:")
		Dim SecondCount As String = (Remainder Mod 60).ToString("00")
		txtRemaining.Text = HourCount & MinuteCount & SecondCount
	End If
End Sub

This works but is too slow; sometimes the display misses an update which usually causes the next update to jump two seconds.

Is there a faster way to do this?

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Answer 1

Hi @RogerSchlueter-7899 ,

Timer ticks aren't precise. Subtracting 1 second per tick accumulates drift and causes jumps when ticks are missed. Instead of decrementing a counter, please try calculating remaining time from a fixed endpoint.

Here is an example based by Copilot:

Private EndTime As DateTime 

Private Sub StartClock(sender As Object, e As RoutedEventArgs) Handles btnStart.Click    
	' Set target end time once     
	EndTime = DateTime.Now.AddSeconds(StartPeriod)     
	tmr = New Timer(1000) With {.AutoReset = True, .Enabled = True}     
	AddHandler tmr.Elapsed, AddressOf UpdateClock
End Sub  

Private Sub PopulateTimer()     
	' Calculate from current time each tick     
	Dim remaining As TimeSpan = EndTime - DateTime.Now    
	If remaining.TotalSeconds > 0 Then         
		txtRemaining.Text = $"{CInt(remaining.TotalHours):00}:{remaining.Minutes:00}:{remaining.Seconds:00}"     
	Else         
		txtRemaining.Text = "00:00:00"         
		tmr.Stop()     
	End If 
End Sub

In this approach, each tick recalculates based on the actual clock time, so any missed or delayed ticks automatically correct on the next update and no error buildup over time.

RogerSchlueter-7899 1,801 Reputation points

2025-12-30T08:14:11.8033333+00:00

Using the EndTime is a good idea and I have implemented it. Thanks.

I am also creating a stop watch where there is no ending time. In that case I set a StartTime then Sub PopulateTimer looks like this:

Private Sub PopulateTimer() Dim Seconds As Long = DateDiff(DateInterval.Second, StartTime, Date.Now) Dim HourCount As String = (CInt(Seconds) \ (60 * 60)).ToString("00:") Dim Remainder As Integer = CInt(Seconds) Mod (60 * 60) Dim MinuteCount As String = (Remainder \ 60).ToString("00:") Dim SecondCount As String = (Remainder Mod 60).ToString("00") txtDuration.Text = HourCount & MinuteCount & SecondCount End Sub

I that how you would do it?