Detecting PC Standby in VB.net

**portreathbeach** · 10-26-2007, 11:19 AM

I have written my own fron-end for my car PC project.

I have a settings.ini file which hold various variables that I need in my project.....winamp path, mp3 path, last played track, last used function.......etc.

I have a sub called writeSettings() which as you would expect writes this file for me. I call this sub whenever I select an item in my main menu or after a certain media file is opened, so the front-end remembers what I was last doing when it is loaded again.

When my shutdown controller tells the computer to shutdown, can I get VB.net to 'see' this and quickly write the settings.ini file, so if the power is completely removed it will know where it last was?

A simpler way would be to keep writing the settings.ini file every 2 or 3 seconds, but would this knacker my hard disk eventually?

Thanks for any help

**Dgege** · 10-26-2007, 11:56 AM

Just a thought, how about you write it only when it's modified?

**alienmanfc6** · 10-26-2007, 02:25 PM

Originally Posted by Dgege

Just a thought, how about you write it only when it's modified?

thats what i did in my front end. every time you change something then it writes the changes

**portreathbeach** · 10-26-2007, 03:04 PM

Thanks for the replies, but the current track position is constantly changing!

I want to be able to have the computer go into standby mode when the ignition is switched off. When the ignition is switched back on within the shutdown time the front-end will load back to where it was before. If the shutdown time expires, the power is completely lost and when the computer boots up the next time, it will load the settings.ini file. This file may have last been written 5 minutes before the time the computer shut down last, therefore the system will not be in the same place that it was last in.....If you get what I mean.

I supose I could write the file every 3 or 4 seconds, therefore if the computer goes into standby mode and then shuts off, it will only be a maximum of 4 seconds behind the track position of when it was last playing.

**alienmanfc6** · 10-26-2007, 03:30 PM

Ok i see what you mean now. I did not know you wanted to save the track pos. I have tried this on mine but could not figure it out so it just starts the track from the begining on reboot. If you figure something out let me know cuz this would be usefull for me but its not that important to me so I not going to waste my time with it.

**portreathbeach** · 10-26-2007, 06:25 PM

As I said in my original post, if there was some way of finding out when Windows is going into standby mode, the settings.ini file could be quickly written then. It takes milliseconds to write the file.

There must be something, but I can't seem to find it on the net. I'll keep looking and trying and post any results here

**Enforcer** · 10-26-2007, 07:58 PM

wm_powerbroadcast is what you are looking for

http://msdn2.microsoft.com/en-us/library/ms704147.aspx

http://msdn2.microsoft.com/en-us/library/Aa373247.aspx

**RickS** · 10-26-2007, 09:43 PM

This should work, I retyped the code since I have it on a different PC so I haven't compiled this to make sure it's all correct but I think it is...

<CODE>
Imports Microsoft.Win32

Public Class Main Form

Private Sub MainForm_Load(ByVal sender as System.Object, ByVal e as System.EventArgs) Handles MyBase.Load
AddHandler SystemEvents.PowerModeChanged, AddressOf MyPMC
End Sub

Private Sub MyPMC(ByVal sender as Object, ByVal e as PowerModeChangedEventArgs)
If e.Mode = PowerModes.Suspend
'Whatever you want to happen when it goes in standby/hibernate goes here
End If
If e.Mode = PowerModes.Resume
'If you want something to happen when it wakes back up, put it here
End If
End Sub

End Class
</CODE>

**portreathbeach** · 10-27-2007, 01:48 PM

Thanks for all of the responses to my post.

This is what I am using....

------------------------------------------------------------------------
Private Const WM_POWERBROADCAST As System.Int32 = &H218
Private Const PBT_APMSUSPEND As System.Int32 = 4

Protected Overrides Sub WndProc(ByRef m As Message)
Select Case m.Msg
Case Is = WM_POWERBROADCAST
Select Case m.WParam.ToInt32
Case Is = PBT_APMSUSPEND
WriteSettings()
Case Else
' When it isn't in suspend mode
End Select
End Select
MyBase.WndProc(m)
End Sub
------------------------------------------------------------------------

Thanks Enforcer.

I played around with RickS code, but I couldn't get it to work on my machine.

Cheers