VB.net errohandling problem

mountainyman

I would like to force my program to continue when it his a particular error.

I would like to handle a Null reference exception at a particular line in my code and only for a sepcific subroutine.

Is this possible?

Thanks

MM

kayos

It would be better to check for the NULL reference before you run the code that would throw the exception. This is simply because from what you say it is a likely case to happen.

Exceptions can be expensive so if you can avoid them do!

mountainyman

I have the below:

Public Class Class1
    Private Sub chkBOX1(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles chkBOX1.CheckedChanged

        Try
            If chkBOX1.Checked = True Then
                txtBOX1.Enabled = True
            End If
            If chkBOX1.Checked = False Then
                txtBOX1.Enabled = False
            End If
        Catch
            MsgBox("You cannot set the BOX Value at this time.")
        End Try
    End Sub
End Class

DublinWriter

A little simpler?...

Public Class Class1
Private Sub chkBOX1(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles chkBOX1.CheckedChanged

Try
txtBOX1.Enabled = chkBOX1.Checked
Catch
MsgBox("You cannot set the BOX Value at this time.")
End Try

End Sub
End Class

kayos

Maybe its me but what the hell is throwing an exception in that? I can only guess it’s the txtbox is null as it has not been created yet and you dynamically add it.

If that’s the case I would be doing

If (txtBOX1 is nothing)
{
MsgBox("You cannot set the BOX Value at this time.")
}
Else
{
txtBOX1.Enabled = chkBOX1.Checked
}

This way you avoid causing an exception and the overhead that incurs, this to me would be the proper way of dealing with this if it is something that you need to allow happen. How ever some VB6 programmers like to use error handling to catch these things rather than check first and avoid the bloody errors.

Would you jump off a ledge without checking to see it was a safe distance?

mountainyman

In fairness Kayos I am doing both. It looks exactly like I am instantiating the checkbox at runtime but I am not.

However I will try adding the chec you reccomend.


Thanks

MM

kayos

mountainyman wrote: »

In fairness Kayos I am doing both. It looks exactly like I am instantiating the checkbox at runtime but I am not.

Sorry if it came across like I was giving out I'm not its just baffling how you can get an exception in that code if both the checkbox (it has to be our you could not click it :P) and txtbox are already there.

I'll still stand by the view if you know it can happen and there is a business case for it happening then check and avoid rather than allow the exception to be thrown.

mountainyman

Thanks to dublin writer and kayos. I checked to see if the control that iis the text box was nothing and it was.

Strange that a designer drawn conrol could be nothing.