Visual Basic

22-Dec-11 22:34

Hello gurus,

I hope someone is around these days, and to everyone who sees this I want to wish a Merry Christmas and a Happy Holiday!

But "let's get down to business": In my application I have to update the form from a different thread, which I do with the following code:

Private Sub UpdateProgress(ByVal value As Integer, ByVal labelText As String)
    If StatusStrip.InvokeRequired Then
	StatusStrip.Invoke(ProgressUpdater, New Object() {value, labelText})      <---- ERROR
    Else
        If value > StatusProgressMain.Maximum Then value = 100
        StatusProgressMain.Value = value
	StatusLabelMain.Text = String.Format("{0} Records", mDVdata.Count)
    End If
End Sub

Unfortunately I run into 'NULL referece exception' when invoking the StatusStrip although neither the value nor the labeltext variables are NULL. Do I probably overlook something like a plain syntax error?

Thank you for reviewing and any hint!
Mick

EDIT / RESOLUTION:
The exception turned out to be thrown in a different part of the procedure, the 'Else' clause: The mDVdata datatable wasn't properly declared!

modified 23-Dec-11 7:05am.

Richard MacCutchan22-Dec-11 22:50

Richard MacCutchan

22-Dec-11 22:50

Which reference gives the exception?

Unrequited desire is character building. OriginalGriff
I'm sitting here giving you a standing ovation - Len Goodman

Sonhospa23-Dec-11 0:16

23-Dec-11 0:16

Hi Richard,

the reference is "Object reference not set to an instance of an object". Would that probably mean that I have to declare another instance of ProgressUpdater? I suppose there's already one instantiated by

Private Delegate Sub AsyncDelegate(ByVal value As Integer, ByVal labelText As String)
Private ProgressUpdater As New AsyncDelegate(AddressOf UpdateProgress)

right at the start of the form class?
Thanks again
Mick

Richard MacCutchan23-Dec-11 0:42

Richard MacCutchan

23-Dec-11 0:42

Michael Schäuble wrote:
the reference is "Object reference not set to an instance of an object".

Yes but which reference? You have an object reference in your code that has not been initialised so you need to look into your code (maybe with the debugger) to find out which it is and why it is still null.

Unrequited desire is character building. OriginalGriff
I'm sitting here giving you a standing ovation - Len Goodman

Sonhospa23-Dec-11 1:02

23-Dec-11 1:02

Thank you, Richard - I put the resolution into the main messages edit. And: You're absolutely right Wink | ;)

!
Merry Christmas again!

Shameel22-Dec-11 23:18

22-Dec-11 23:18

I suspect that the ProgressUpdater delegate might not have been initialized.

Sonhospa23-Dec-11 0:05

23-Dec-11 0:05

Hi Shameel,

I have these two lines right at the beginning of the class:

Private Delegate Sub AsyncDelegate(ByVal value As Integer, ByVal labelText As String)
Private ProgressUpdater As New AsyncDelegate(AddressOf UpdateProgress)

Would that be sufficient?

Shameel23-Dec-11 0:31

23-Dec-11 0:31

Michael Schäuble wrote:
Would that be sufficient?

Should be.

Can you check which element of your code is throwing the null reference exception? If your StatusStrip is itself null, then your designer generated code might be screwed up.

Sonhospa23-Dec-11 0:36

23-Dec-11 0:36

But in that case the If-clause would throw the exception, wouldn't it?

Shameel23-Dec-11 1:02

23-Dec-11 1:02

Michael Schäuble wrote:

But in that case the If-clause would throw the
exception, wouldn't it?

Yes, it usually would. But it is also possible that the Invoked method is throwing the error and since it does not have a Try Catch block, it is being pushed backed up the stack. Add Try Catch and some custom logging to find out where the problem exactly is.

Sonhospa23-Dec-11 1:03

23-Dec-11 1:03

Thank's for your help, Shameel. I found it out and put the answer into the main message as an edit.
Merry Christmas again!

Shameel23-Dec-11 1:45