Structures question (vb.net)

[Karzack]

Hello, Im new to programming in general. Did a little on apple IIE's but that wasn't much. I have desiced to try to learn again with vb.net and ran into something. I'm learning with the "Visual Basic .NET Step by Step" book.

 

When I try to add a value to a variable in a structure I get an error.

 

An unhandled exception of type 'System.NullReferenceException'

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

 

Example: Trying to make a small address book.

This structure and the sub are in the module.

frmAdd is the form that information is added to the address book.

  Structure Person
       Public firstName As String
       Public middleName As String
       Public lastName As String
       Public homeNumber As String
       Public email As String
       Public address As String
       Public city As String
       Public state As String
       Public workNumber As String
       Public cellNumber As String
       Public photo As Image
   End Structure

   Public page() As Person        ' Array for number of people in book
   Public pg As Short             ' value to determine how many pages

   Sub pageFill()
       page(pg).firstName = frmAdd.txtFirstName.Text             ' < error here
       page(pg).middleName = frmAdd.txtMiddleName.Text
       page(pg).lastName = frmAdd.txtLastName.Text
       page(pg).homeNumber = frmAdd.txtHomeNumber.Text
  end sub

 

Didn't put in the rest of the sub because it was the same as the first few lines.

Anyway. When I type in the values in the text boxes and hit the button that calles this sub. I get the error described above. At the first line of the sub.

 

I think I need to back off coding for now, I have a headache. :(

I have done some tread searching but didn't come up with anything.

[MikeJ]

It doesn't appear as if you have told the program what pg is or how many items the array will hold. Is there any other part of this code, such as a ReDim statement, or where you are setting the variable pg?

 

If not, before you are able to get to the array, you will need to ReDim it to let it hold a certain number of elements, and then you will need to define pg with a value to access the particular part of the array.

[Karzack]

*sighs*

 

I just forgot to redim the array. :o Thank you.

Value for pg was set before sub was called.

 

*muddles under his breath*