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Trial system

Posted on 1998-07-24
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Last Modified: 2010-05-03
Anybody got some sample code for a twenty day trial system?

Rob.
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Question by:robjgreen
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Expert Comment

by:MikeP090797
ID: 1466614
What do you mean? A program that will run for only 20 days since it's installation? How well protected should it be?
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by:robjgreen
ID: 1466615
The user should not be able to stop it from expiring...
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MikeP090797 earned 100 total points
ID: 1466616
The general approach would be to store the installation in the registry, using DateValue so it will be stored as a long number and not as a readable date, and compare it to today's date. If the difference is more then 20 days, exit. If the date in the registry isn't found, exit. If you are planning it for the average user, using SaveSetting will be enough, he won't be able to modify the date. If you are planning it for high level experts, you should use Reg* APIs to store it elsewhere so noone will figure out it's your program, or store it in a file like prog10xs.dll in \windows\system directory, so the user won't figure it out either. Make the file 20KB long, so it won't look suspicious
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Author Comment

by:robjgreen
ID: 1466617
Hi Mike,
   Well, that is actually what I had done already, simply stored it in the registry... but I'm going to test your DateValue idea before I accept the answer (low on points!)

Kind Regs,
Rob Green.
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Expert Comment

by:MikeP090797
ID: 1466618
Sorry, I posted it to early. DateValue won't do it, but you can store it like Day*10+Month*500+Year*7000
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Author Comment

by:robjgreen
ID: 1466619
Hi Mike,
   it seems to be working okay... I'll have to get a decent install program that can set these things up though.

Kind Regards,
Rob Green.
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Author Comment

by:robjgreen
ID: 1466620
Mike, erm... well I used this code:

Private Sub Form_Load()
    Dim installdat, currentdate As Long
    frmUnReg.Picture = frmSplash.Picture
    installdate = GetSetting("Heatwave Creations", "PasswordSafe", "gg1", "")
    currentdate = DateValue(Date)
    difference = currentdate - installdate
End Sub

Private Sub Timer1_Timer()
    If (20 - difference) > 0 Then
        frmPasswordSafe.Visible = True
        frmPasswordSafe.Enabled = False
        frmLogin.Visible = True
        Unload Me
    ElseIf (20 - difference) <= 0 Then
        MsgBox "Your Trial Has Expired"
        frmPreferences.Visible = True
        Unload Me
    End If
End Sub

But it doesnt work, it claims I have 40 days remaining!

Can you write me a code example please?

Kind Regards,
Rob Green.
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Expert Comment

by:MikeP090797
ID: 1466621
Try something like:
Dim InstallDate as date
installdate = GetSetting("Heatwave Creations", "PasswordSafe", "gg1", "")

If DateDiff("m", Now, InstallDate)>20 then
'Exit
else
'Continue
End if
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Author Comment

by:robjgreen
ID: 1466622
Its okay, I rewrote all the code and it works okay now...
Cant remember what was wrong... too noisy here to think.
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