Why This Error

[WackoWolf]

I don't understand why I am getting this error when I try and run the program. This is just a smiple program I am trying to do from the book, but I am useing my own database. I am getting this error "An unhandled exception of type 'System.NullReferenceException' occurred in DVD Inventory.exe" If I rem the line out, the show is wasted, I want the show to work. Any help would be nice.


And this is the line of code that it is doing it with.

Can someone tell me what in the world I am doing worng. I am makeing this for my self, but am trying to see if I can get the database to work. Then I will be adding to the program, and changing it.

Thank You
WackoWolf

[SIZE=2][COLOR=#0000ff]Private[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Sub[/COLOR][/SIZE][SIZE=2] ShowPosition()
lblPosition.Text = "Record " & currManager.Position + 1 & " of " & currManager.Count
[/SIZE][SIZE=2][COLOR=#0000ff]End[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Sub
[/COLOR][/SIZE]

This is all the code.

[SIZE=2][COLOR=#0000ff]
[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Dim[/COLOR][/SIZE][SIZE=2] currManager [/SIZE][SIZE=2][COLOR=#0000ff]As[/COLOR][/SIZE][SIZE=2] CurrencyManager
[/SIZE][SIZE=2][COLOR=#0000ff]Dim[/COLOR][/SIZE][SIZE=2] lblPosition [/SIZE][SIZE=2][COLOR=#0000ff]As[/COLOR][/SIZE][SIZE=2] Label
 
 
[/SIZE][SIZE=2][COLOR=#0000ff]Private[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Sub[/COLOR][/SIZE][SIZE=2] frmMain_Load([/SIZE][SIZE=2][COLOR=#0000ff]ByVal[/COLOR][/SIZE][SIZE=2] sender [/SIZE][SIZE=2][COLOR=#0000ff]As[/COLOR][/SIZE][SIZE=2] System.Object, [/SIZE][SIZE=2][COLOR=#0000ff]ByVal[/COLOR][/SIZE][SIZE=2] e [/SIZE][SIZE=2][COLOR=#0000ff]As[/COLOR][/SIZE][SIZE=2] System.EventArgs) [/SIZE][SIZE=2][COLOR=#0000ff]Handles[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]MyBase[/COLOR][/SIZE][SIZE=2].Load
 
CONDVD.Fill(Condvd1)
 
currManager = BindingContext(Condvd1, "Media")
 
ShowPosition()
 
[/SIZE][SIZE=2][COLOR=#0000ff]End[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Sub[/COLOR][/SIZE]
[SIZE=2][COLOR=#0000ff]
[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Private[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Sub[/COLOR][/SIZE][SIZE=2] bntPrevious_Click([/SIZE][SIZE=2][COLOR=#0000ff]ByVal[/COLOR][/SIZE][SIZE=2] sender [/SIZE][SIZE=2][COLOR=#0000ff]As[/COLOR][/SIZE][SIZE=2] System.Object, [/SIZE][SIZE=2][COLOR=#0000ff]ByVal[/COLOR][/SIZE][SIZE=2] e [/SIZE][SIZE=2][COLOR=#0000ff]As[/COLOR][/SIZE][SIZE=2] System.EventArgs) [/SIZE][SIZE=2][COLOR=#0000ff]Handles[/COLOR][/SIZE][SIZE=2] bntPrevious.Click[/SIZE]
[SIZE=2]
currManager.Position -= 1
 
ShowPosition()
 
[/SIZE][SIZE=2][COLOR=#0000ff]End[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Sub[/COLOR][/SIZE]
[SIZE=2][COLOR=#0000ff]
[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Private[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Sub[/COLOR][/SIZE][SIZE=2] bntNext_Click([/SIZE][SIZE=2][COLOR=#0000ff]ByVal[/COLOR][/SIZE][SIZE=2] sender [/SIZE][SIZE=2][COLOR=#0000ff]As[/COLOR][/SIZE][SIZE=2] System.Object, [/SIZE][SIZE=2][COLOR=#0000ff]ByVal[/COLOR][/SIZE][SIZE=2] e [/SIZE][SIZE=2][COLOR=#0000ff]As[/COLOR][/SIZE][SIZE=2] System.EventArgs) [/SIZE][SIZE=2][COLOR=#0000ff]Handles[/COLOR][/SIZE][SIZE=2] bntNext.Click[/SIZE]
[SIZE=2]
currManager.Position += 1
 
ShowPosition()
 
[/SIZE][SIZE=2][COLOR=#0000ff]End[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Sub[/COLOR][/SIZE]
[SIZE=2][COLOR=#0000ff]
[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Private[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Sub[/COLOR][/SIZE][SIZE=2] bntFirst_Click([/SIZE][SIZE=2][COLOR=#0000ff]ByVal[/COLOR][/SIZE][SIZE=2] sender [/SIZE][SIZE=2][COLOR=#0000ff]As[/COLOR][/SIZE][SIZE=2] System.Object, [/SIZE][SIZE=2][COLOR=#0000ff]ByVal[/COLOR][/SIZE][SIZE=2] e [/SIZE][SIZE=2][COLOR=#0000ff]As[/COLOR][/SIZE][SIZE=2] System.EventArgs) [/SIZE][SIZE=2][COLOR=#0000ff]Handles[/COLOR][/SIZE][SIZE=2] bntFirst.Click[/SIZE]
 
[SIZE=2]currManager.Position = 0[/SIZE]
[SIZE=2]
ShowPosition()
 
[/SIZE][SIZE=2][COLOR=#0000ff]End[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Sub[/COLOR][/SIZE]
[SIZE=2][COLOR=#0000ff]
[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Private[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Sub[/COLOR][/SIZE][SIZE=2] bntLast_Click([/SIZE][SIZE=2][COLOR=#0000ff]ByVal[/COLOR][/SIZE][SIZE=2] sender [/SIZE][SIZE=2][COLOR=#0000ff]As[/COLOR][/SIZE][SIZE=2] System.Object, [/SIZE][SIZE=2][COLOR=#0000ff]ByVal[/COLOR][/SIZE][SIZE=2] e [/SIZE][SIZE=2][COLOR=#0000ff]As[/COLOR][/SIZE][SIZE=2] System.EventArgs) [/SIZE][SIZE=2][COLOR=#0000ff]Handles[/COLOR][/SIZE][SIZE=2] bntLast.Click[/SIZE]
[SIZE=2]
currManager.Position = currManager.Count - 1
ShowPosition()
 
[/SIZE][SIZE=2][COLOR=#0000ff]End[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Sub[/COLOR][/SIZE]
[SIZE=2][COLOR=#0000ff]
[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Private[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Sub[/COLOR][/SIZE][SIZE=2] ShowPosition()[/SIZE]
[SIZE=2]
lblPosition.Text = "Record " & currManager.Position + 1 & " of " & currManager.Count
 
[/SIZE][SIZE=2][COLOR=#0000ff]End[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Sub[/COLOR][/SIZE]
[SIZE=2][COLOR=#0000ff]
[/COLOR][/SIZE][SIZE=2]
[/SIZE][SIZE=2][COLOR=#0000ff]Private[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Sub[/COLOR][/SIZE][SIZE=2] bntExit_Click([/SIZE][SIZE=2][COLOR=#0000ff]ByVal[/COLOR][/SIZE][SIZE=2] sender [/SIZE][SIZE=2][COLOR=#0000ff]As[/COLOR][/SIZE][SIZE=2] System.Object, [/SIZE][SIZE=2][COLOR=#0000ff]ByVal[/COLOR][/SIZE][SIZE=2] e [/SIZE][SIZE=2][COLOR=#0000ff]As[/COLOR][/SIZE][SIZE=2] System.EventArgs) [/SIZE][SIZE=2][COLOR=#0000ff]Handles[/COLOR][/SIZE][SIZE=2] bntExit.Click[/SIZE]
[SIZE=2]
Beep()
 
[/SIZE][SIZE=2][COLOR=#0000ff]End[/COLOR][/SIZE]
[SIZE=2][COLOR=#0000ff]
[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]End[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Sub
End[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Class[/COLOR][/SIZE]

 

[WackoWolf]

I don't understand why I am getting this error when I try and run the program. This is just a smiple program I am trying to do from the book, but I am useing my own database. I am getting this error when I try to use "ShowPosition()" And this is the error I get. "An unhandled exception of type 'System.NullReferenceException' occurred in DVD Inventory.exe" If I rem the line out, the show is wasted but the program will work, I want the showPosition() function to work. Any help would be nice.

And this is the line of code that it is doing it with.

[LEFT][SIZE=2][COLOR=#0000ff]Private[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Sub[/COLOR][/SIZE][SIZE=2] ShowPosition()[/LEFT]
lblPosition.Text = "Record " & currManager.Position + 1 & " of " & currManager.Count
[/SIZE][SIZE=2][COLOR=#0000ff]End[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Sub[/COLOR][/SIZE]
[SIZE=2][COLOR=#0000ff]

[/COLOR][/SIZE]

​

 

[Schenz]

Is currManager declared globally for the form, or just in the calling subroutine?

 

[WackoWolf]

This is what I have declare globally in the program.

[SIZE=2][COLOR=#0000ff]
[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Dim[/COLOR][/SIZE][SIZE=2] currManager [/SIZE][SIZE=2][COLOR=#0000ff]As[/COLOR][/SIZE][SIZE=2] CurrencyManager
[/SIZE][SIZE=2][COLOR=#0000ff]Dim[/COLOR][/SIZE][SIZE=2] lblPosition [/SIZE][SIZE=2][COLOR=#0000ff]As[/COLOR][/SIZE][SIZE=2] Label
[/SIZE][SIZE=2][COLOR=#0000ff]Dim[/COLOR][/SIZE][SIZE=2] SaveDiskName, SaveDiskID, SaveCategory, SaveQuantity [/SIZE][SIZE=2][COLOR=#0000ff]As [/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]String
[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Dim[/COLOR][/SIZE][SIZE=2] edit [/SIZE][SIZE=2][COLOR=#0000ff]As [/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Boolean
[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Dim[/COLOR][/SIZE][SIZE=2] Mboxmessage [/SIZE][SIZE=2][COLOR=#0000ff]As [/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]String[/COLOR][/SIZE]

 

[jmcilhinney]

Nowhere in that code have you assigned an object to the 'lblPosition' variable. It is a null reference, i.e. it refers to no object, so you cannot access the Text property of an object through it. You would normally not declare a Label variable like that. Normally you would add it to your form in the designer.

 

[WackoWolf]

How would I go about Adding it to the form in design time? Or is there a way to fix it to work with the way I have it now?

Thank You
WackoWolf

 

[jmcilhinney]

Please ask each question in one thread only. I answered your other thread and then I found this one, so you've got people answering the same question in two different places, not knowing if someone has already said the same thing in the other. Do your part to keep the forums ordered and as easy to use for everyone as possible. I have now merged your two threads into this one.

 

[WackoWolf]

Thank You, I am sorry for the way I first posted the question, I now understand that I need to post in the right form.

WackoWolf

 

[jmcilhinney]

How would I go about Adding it to the form in design time? Or is there a way to fix it to work with the way I have it now?

Thank You
WackoWolf

Have you never added a control to a form in the designer before? It would be easier to delete the declaration you currently have and just add a Label in the designer with the same name. The alternative is to create a new Lable object in code and assign it to the variable, then set the relevant properties and add it to the form's Controls collection.

 

[WackoWolf]

Now I really feel dumb for the way I did this thing, keep saying to myself that it needed a lable to work. I will try that now.

Thanks
WackoWolf