Contatore a parire da..

Public Class Form1
    Dim Inizio As Date = Now
    Dim TempoTrascorso As TimeSpan


    Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
        Inizio = Now
        Timer1.Interval = 100
        Timer1.Enabled = True

    End Sub

    Private Sub Timer1_Tick(sender As System.Object, e As System.EventArgs) Handles Timer1.Tick
        TempoTrascorso = Now - Inizio
        Me.Ore.Text = TempoTrascorso.Hours.ToString.PadLeft(2, "0"c)
        Me.Min.Text = TempoTrascorso.Minutes.ToString.PadLeft(2, "0"c)
        Me.Sec.Text = TempoTrascorso.Seconds.ToString.PadLeft(2, "0"c)
        Me.Mil.Text = TempoTrascorso.Milliseconds.ToString.PadLeft(3, "0"c)

    End Sub
End Class

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Private alarmTime As Date
    Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
        Me.alarmTime = Date.Now.AddMinutes(45)
        Me.Timer2.Start()
    End Sub

    Private Sub Timer2_Tick(sender As System.Object, e As System.EventArgs) Handles Timer2.Tick
        If alarmTime < Date.Now Then
            Me.Timer2.Stop()
            MessageBox.Show("Tempo scaduto")
        Else

        
        Dim remainingTime As TimeSpan = Me.alarmTime.Subtract(Date.Now)

        Me.Label1.Text = String.Format("{0}:{1:d2}:{2:d2}", _
                                       remainingTime.Hours, _
                                       remainingTime.Minutes, _
                                       remainingTime.Seconds)
        End If
    End Sub