[Resolved]Object Instance Error

[Pc_Madness]

'from the AlphaNumericButton usercontrol
Public Function getChr() As String
       If IsAlphabetic = False Then
           getChr = strDigitValue
       Else
           If keyPadTimer.Enabled = True Then
              'supposed to be working with this bit
               Dim tmpArray() As String
               Dim i As Integer
               For i = 0 To Len(strAlphaValue)
                   tmpArray(i) = strAlphaValue.Substring(i, 1)
               Next
               For i = 0 To tmpArray.Length
                   MsgBox(tmpArray(i))
               Next
               getChr = ""
               'end this bit
           Else
               If strAlphaValue.Length > 0 Then
                   getChr = strAlphaValue.Substring(0, 1)
               Else
                   getChr = " "
               End If
           End If
       End If
   End Function
 
 
 
 
 
Private Sub btnKey2to9Handler(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnKey2.Click, btnKey3.Click
 
       If armed = True Or expectingInput = True Then
           Static KeyValue As String
           MsgBox(sender.name)
           If Not lastKeyPressed Is sender Then
               AlphaNumericButton.keyPadTimer.Enabled = False
           End If
           lastKeyPressed = sender
 
           If AlphaNumericButton.IsAlphabetic = False Then
               KeyValue = sender.Getchr
           Else
 
              'Working with this part
               If Not AlphaNumericButton.keyPadTimer.Enabled Then
                   KeyValue = sender.Getchr
                   AlphaNumericButton.keyPadTimer.Enabled = True
               Else
                   'Delete the last alpha character.
                   If inputBuffer.Length > 0 Then
                       inputBuffer = inputBuffer.Substring(0, inputBuffer.Length - 1)
                   End If
                   'Determine the next alpha character.
 
                   'Errors here if I click within one second
                   MsgBox(sender.Getchr)
               End If
           End If
 
       End If
   End Sub

Howdy folks.

My little usercontrol has a problem (), it completely crashes when I try to use sender.GetChr.(the Getchr function will recieve and return values when its finished) Basically I have a sub which handles the click events for 10 AlphaNumericButton controls (top code is from that), and they have to retrieve a value using the Getchr function. Theres a timer which is shared across all of the usercontrols called keypadtimer (which is inside the control) which is set for 1 second. So the first time I click, the timer not enabled part fires and works properly. If I wait longer than 1 second, it'll work fine again... but if I click before 1 second has elapsed, I get the following error on the Msgbox part,

An unhandled exception of type 'System.NullReferenceException' occurred in microsoft.visualbasic.dll

Additional information: Object reference not set to an instance of an object.

Anyone?

[Edneeis]

It sounds like sender or something else is not set to anything. You should test if sender is Nothing before trying to use it. It's also a good idea to cast it to a strong type instead of using the generic object type especially since object doesn't have a name property. Depending on what it is it may not have a GetChr method either.

[plenderj]

Use the Debug "Solution Configuration" and then run it from the IDE. What line do you get the error on?

[Pc_Madness]

Originally posted by Edneeis
It sounds like sender or something else is not set to anything. You should test if sender is Nothing before trying to use it. It's also a good idea to cast it to a strong type instead of using the generic object type especially since object doesn't have a name property. Depending on what it is it may not have a GetChr method either.

Well, I tried to do If sender <> Nothing Then and it had a spaz about that, but after it highlighted the error, sender wasn't empty, and since that part of the code will only occur when the error posted above would occur, I think we can assume that it isn't empty.

And Jamie, the error is on the Msgbox (the second one) line in the btnKey2to9Handler sub.

[plenderj]

Try this :

Private Sub btnKey2to9Handler(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnKey2.Click, btnKey3.Click
[b]    MsgBox(sender Is Nothing)[/b]
 
       If armed = True Or expectingInput = True Then
           Static KeyValue As String
           If Not lastKeyPressed Is sender Then
               AlphaNumericButton.keyPadTimer.Enabled = False
           End If
           lastKeyPressed = sender
 
           If AlphaNumericButton.IsAlphabetic = False Then
               KeyValue = sender.Getchr
           Else
 
              'Working with this part
               If Not AlphaNumericButton.keyPadTimer.Enabled Then
                   KeyValue = sender.Getchr
                   AlphaNumericButton.keyPadTimer.Enabled = True
               Else
                   'Delete the last alpha character.
                   If inputBuffer.Length > 0 Then
                       inputBuffer = inputBuffer.Substring(0, inputBuffer.Length - 1)
                   End If
                   'Determine the next alpha character.
 
                   'Errors here if I click within one second
[b]    MsgBox(sender Is Nothing)[/b]
                   MsgBox(sender.Getchr)
               End If
           End If
 
       End If
   End Sub

If it says false, then the problem might lie in an unhandled exception in the Getchr() method.
I have never used UserControls, but there is the possibility that unhandled exceptions in UserControls are passed up through the call stack - instead of VB catching and showing you the error there.

Try using MsgBox() statements in the Getchr() method to track its progress...

[Pc_Madness]

The Msgbox's return false, and it seems it hates the two loops inside the GetChr() function.

[Pc_Madness]

Woohoo, got it! Thanks Jamie. I shall name my least liked child in your honour.

[plenderj]

Let me guess - you never ReDimmed your tmpArray array ?

[Pc_Madness]

Well, that and you can't use substring(0, 1), but I've cheated and just set it to array to 4 items and use mid instead due to substring's oddity (even when I did i + 1 )