Using the Timer Control

' --- Designer setup (set in Properties window) ---
' Timer1.Interval = 1000   ' 1 second
' Timer1.Enabled  = False  ' don't start until user clicks

' --- Start / Stop from buttons ---
Private Sub btnStart_Click(...) Handles btnStart.Click
    Timer1.Start()              ' same as Timer1.Enabled = True
    btnStart.Enabled = False
    btnStop.Enabled  = True
End Sub

Private Sub btnStop_Click(...) Handles btnStop.Click
    Timer1.Stop()               ' same as Timer1.Enabled = False
    btnStart.Enabled = True
    btnStop.Enabled  = False
End Sub

' --- The Tick handler ---
Private Sub Timer1_Tick(sender As Object, e As EventArgs) Handles Timer1.Tick
    ' This runs every Interval ms on the UI thread — safe to update controls
    lblClock.Text = DateTime.Now.ToString("HH:mm:ss")
End Sub

' --- Change interval at runtime ---
Timer1.Stop()
Timer1.Interval = 500   ' change to 0.5 s
Timer1.Start()

' --- One-shot delay (fire once, then stop) ---
Private Sub ShowSplashThenHide()
    frmSplash.Show()
    Timer1.Interval = 3000   ' 3 seconds
    Timer1.Start()
End Sub

Private Sub Timer1_Tick(...) Handles Timer1.Tick
    Timer1.Stop()              ' stop immediately — runs only once
    frmSplash.Hide()
End Sub

Private _secondsLeft As Integer

Private Sub btnStartCountdown_Click(...) Handles btnStartCountdown.Click
    _secondsLeft = CInt(nudSeconds.Value)    ' set from NumericUpDown
    If _secondsLeft < 1 Then Return
    UpdateCountdownDisplay()
    Timer1.Interval = 1000
    Timer1.Start()
    btnStartCountdown.Enabled = False
    btnReset.Enabled          = True
End Sub

Private Sub Timer1_Tick(...) Handles Timer1.Tick
    _secondsLeft -= 1
    UpdateCountdownDisplay()
    If _secondsLeft <= 0 Then
        Timer1.Stop()
        lblDisplay.Text = "TIME'S UP!"
        btnStartCountdown.Enabled = True
        SystemSounds.Beep.Play()      ' play system beep
    End If
End Sub

Private Sub UpdateCountdownDisplay()
    Dim mins = _secondsLeft \ 60
    Dim secs = _secondsLeft Mod 60
    lblDisplay.Text = $"{mins:D2}:{secs:D2}"
    ' Change colour when under 10 seconds
    lblDisplay.ForeColor = If(_secondsLeft <= 10, Color.Red, Color.LimeGreen)
End Sub

Private Sub btnReset_Click(...) Handles btnReset.Click
    Timer1.Stop()
    _secondsLeft = 0
    lblDisplay.Text = "00:00"
    lblDisplay.ForeColor = Color.LimeGreen
    btnStartCountdown.Enabled = True
    btnReset.Enabled          = False
End Sub

Imports System.Diagnostics

Private _sw As New Stopwatch()
Private _lapTimes As New List(Of TimeSpan)

Private Sub btnStart_Click(...) Handles btnStart.Click
    _sw.Start()          ' resumes if already running
    Timer1.Interval = 50 ' update display 20× per second
    Timer1.Start()
    btnStart.Enabled = False
    btnStop.Enabled  = True
End Sub

Private Sub btnStop_Click(...) Handles btnStop.Click
    _sw.Stop()
    Timer1.Stop()
    btnStart.Enabled = True
    btnStop.Enabled  = False
End Sub

Private Sub btnReset_Click(...) Handles btnReset.Click
    _sw.Reset()               ' stops and zeroes the stopwatch
    Timer1.Stop()
    _lapTimes.Clear()
    lstLaps.Items.Clear()
    lblDisplay.Text = "00:00.000"
End Sub

Private Sub btnLap_Click(...) Handles btnLap.Click
    If Not _sw.IsRunning Then Return
    _lapTimes.Add(_sw.Elapsed)
    lstLaps.Items.Add($"Lap {_lapTimes.Count}: {_sw.Elapsed:mm\:ss\.fff}")
End Sub

Private Sub Timer1_Tick(...) Handles Timer1.Tick
    ' Timer updates display; Stopwatch measures time
    Dim ts = _sw.Elapsed
    lblDisplay.Text = $"{ts.Minutes:D2}:{ts.Seconds:D2}.{ts.Milliseconds:D3}"
End Sub

' --- Animated progress bar (simulating a long task) ---
Private _progress As Integer = 0

Private Sub btnBeginTask_Click(...) Handles btnBeginTask.Click
    _progress = 0
    progressBar1.Value = 0
    Timer1.Interval    = 80    ' tick every 80 ms
    Timer1.Start()
    btnBeginTask.Enabled = False
End Sub

Private Sub Timer1_Tick(...) Handles Timer1.Tick
    _progress += 2             ' 2% per tick → 100% in 50 ticks × 80ms = 4 s
    progressBar1.Value = Math.Min(_progress, 100)
    lblPercent.Text    = $"{_progress}%"
    If _progress >= 100 Then
        Timer1.Stop()
        lblPercent.Text      = "Complete!"
        btnBeginTask.Enabled = True
    End If
End Sub

' --- Auto-refresh dashboard every 5 seconds ---
Private Sub Form_Load(...) Handles MyBase.Load
    RefreshDashboard()                  ' show data immediately
    Timer1.Interval = 5000
    Timer1.Start()                      ' refresh every 5 s
End Sub

Private Sub Timer1_Tick(...) Handles Timer1.Tick
    RefreshDashboard()
End Sub

Private Sub RefreshDashboard()
    lblLastUpdated.Text = $"Updated: {DateTime.Now:HH:mm:ss}"
    ' ... load from database, API, sensor, etc.
End Sub

' --- Blinking label alert ---
Private Sub Timer1_Tick(...) Handles Timer1.Tick
    lblAlert.Visible = Not lblAlert.Visible   ' toggle every Tick
End Sub

' Three timers with different rates on one form

' Timer1 — 1000 ms — update clock label
Private Sub Timer1_Tick(...) Handles Timer1.Tick
    lblClock.Text = DateTime.Now.ToString("HH:mm:ss")
End Sub

' Timer2 — 50 ms — smooth animation repaint
Private Sub Timer2_Tick(...) Handles Timer2.Tick
    picCanvas.Invalidate()   ' ~20 fps
End Sub

' Timer3 — 30000 ms — poll database / API
Private Sub Timer3_Tick(...) Handles Timer3.Tick
    LoadLatestDataAsync()
End Sub

' --- Precise elapsed time with Stopwatch ---
Dim sw As New System.Diagnostics.Stopwatch()

Private Sub btnBenchmark_Click(...) Handles btnBenchmark.Click
    sw.Restart()                    ' reset and start in one call
    DoExpensiveWork()
    sw.Stop()
    lblTime.Text = $"Elapsed: {sw.ElapsedMilliseconds} ms"
    ' For sub-millisecond: sw.ElapsedTicks / Stopwatch.Frequency
End Sub

' --- Avoid UI freezes: don't do heavy work in Tick ---
' BAD:  Thread.Sleep(5000) inside Tick freezes the UI
' GOOD: Start an Async task and await it, or use BackgroundWorker
Private Async Sub Timer1_Tick(...) Handles Timer1.Tick
    Timer1.Stop()                   ' prevent re-entrancy
    Await LoadDataAsync()           ' non-blocking await
    Timer1.Start()
End Sub