Run timer in background in visual basic form - vb.net

Question

first I'm new in this, and I have this code that shows a prompt to restart or postpone the restart for a while, the issue is that i want to hide the message and bring it back after the time specified by the user.
I'm using a "visual basic form" and the time that restart will be postponed it's selected from a "ComboBox"
My code is as follows.
Imports System.Management
Imports System.Security.Permissions
Imports System
Imports System.IO
Imports System.Collections
Imports System.SerializableAttribute
Public Class Form2
Dim PostponeReboot As Integer = 50
Private Const CP_NOCLOSE_BUTTON As Integer = &H200
Protected Overloads Overrides ReadOnly Property CreateParams() As CreateParams
Get
Dim myCp As CreateParams = MyBase.CreateParams
myCp.ClassStyle = myCp.ClassStyle Or CP_NOCLOSE_BUTTON
Return myCp
End Get
End Property
Private Sub Form2_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Form1.Hide()
Label4.Text = SystemInformation.UserName
Button1.Enabled = False
ComboBox1.Enabled = False
Timer1.Interval = 1000
End Sub
Private Sub CheckBox1_CheckedChanged(sender As Object, e As EventArgs) Handles CheckBox1.CheckedChanged
If CheckBox1.Checked Then
CheckBox2.Enabled = False
Button1.Enabled = True
ComboBox1.Enabled = False
ElseIf CheckBox1.Checked = 0 Then
CheckBox2.Enabled = True
Button1.Enabled = False
ComboBox1.Enabled = False
End If
End Sub
Private Sub CheckBox2_CheckedChanged(sender As Object, e As EventArgs) Handles CheckBox2.CheckedChanged
If CheckBox2.Checked Then
CheckBox1.Enabled = False
ComboBox1.Enabled = True
Button1.Enabled = True
ElseIf CheckBox2.Checked = 0 Then
CheckBox1.Enabled = True
ComboBox1.Enabled = False
Button1.Enabled = False
End If
End Sub
Private Sub ComboBox1_SelectedIndexChanged(ByVal sender As System.Object, e As EventArgs) Handles ComboBox1.SelectedIndexChanged
If ComboBox1.Text = "1 Hora" Then
PostponeReboot = 10
ElseIf ComboBox1.Text = "2 Horas" Then
PostponeReboot = 20
ElseIf ComboBox1.Text = "4 Horas" Then
PostponeReboot = 40
ElseIf ComboBox1.Text = "Seleccione" Then
Button1.Enabled = False
End If
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
If CheckBox1.Checked Then
MessageBox.Show("Rebooting")
'Shell("shutdown -r -f -t 60")
Form1.Close()
End
ElseIf CheckBox2.Checked Then
MessageBox.Show(PostponeReboot)
Timer1.Start()
Me.Hide()
End If
If PostponeReboot = 0 Then
Me.Show()
Else
Me.Hide()
End If
End Sub
Private Sub Timer1_Tick(sender As Object, e As EventArgs) Handles Timer1.Tick
PostponeReboot = PostponeReboot - 1
'Label5.Text = PostponeReboot
End Sub
End Class
In the first "If" sentence of below I want to start the timer and hide the form, and in the second "If" i want to bring it back the form, but the form remains hidden.
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
If CheckBox1.Checked Then
MessageBox.Show("Rebooting")
'Shell("shutdown -r -f -t 60")
Form1.Close()
End
ElseIf CheckBox2.Checked Then
MessageBox.Show(PostponeReboot)
Timer1.Start()
Me.Hide()
End If
If PostponeReboot = 0 Then
Me.Show()
Else
Me.Hide()
End If
End Sub
I've tried putting the second "If" sentence in another place but don't work, what I'm doing wrong.

Answer 1

I assume here that your Timer1 class raises the Timer1.Tick event every x time after Timer1.Start() is called. The fact that the form can hide tells me Timer1.Start() isn't a blocking method. As such, your second if statement will be verified right after you hide the form, without waiting for the PostponeReboot variable to reach zero. This particular button handler would then exit and your form would remain hidden. What I see is that you already have an event handler for each tick of your timer. Why not use this handler to verify the state of your PostponeReboot variable?
Private Sub Timer1_Tick(sender As Object, e As EventArgs) Handles Timer1.Tick
PostponeReboot = PostponeReboot - 1
If PostponeReboot = 0 Then
Timer1.Stop() 'I would assume
Me.Show()
End If
End Sub
Although, I would recommend you to try other solutions, like having your timer raise an event only when it reaches the elapsed time (so you don't have to handle each ticks unnecessarily). I would also recommend looking into an Universal Windows App with Toast Notifications as you could set a Notification to appear at a set time (handled by Windows) so that you don't have to have a thread running in the background for this.