Question array initialization, way simple

[jamie123]

I dont' know why I can't figure this out, but I don't wanna spend anymore time on it and I know someone knows the answer here. Very simple question. Here's my code:

  Dim companyids(200) As String

     myReader = File.OpenText(ComboBox1.Text + "SPE\DI_IR.upc")
                For i As Integer = 1 To diskdirlines
                    companyids(i) = myReader.ReadLine().Substring(2, 4)
                Next

I don't want to dim companyids with an index of 200, I would like it to only initialize as many elements as it needs. But I can't figure out how to initialize it without putting in all of the elements at once (impossible, it must run through that loop) or putting in a static index like I have done above. How can I initialize this array so that its number of elements is dynamic and can change everytime?

Thanks!

 

[bdinnocenzo]

I'm not sure I understand your problem, so here's my best answer to what I think you're asking...

First when you initialize the string array companyids with 200, you are actually creating an array of 201 elements -- arrays are zero based so you've created elements 0 to 200 or 201 all together. You can create a dynamic array that can be changed during runtime like this:

Dim companyids() as String

then prior to using the array you can re-dimension it and load it like this:

myReader = File.OpenText(ComboBox1.Text + "SPE\DI_IR.upc")
ReDim companyids(diskdirlines - 1)
For i As Integer = 0 To diskdirlines - 1
companyids(i) = myReader.ReadLine().Substring(2, 4)
Next

This way the array companyids can be whatever size it needs to be to accommodate your needs.

 

[JohnH]

It is better if you use a list, it is a dynamic array. If the size is known ReDim statement could be better.

Dim companyids As New List(Of String)
Do Until myReader.EndOfStream
    companyids.Add(myReader.ReadLine().Substring(2, 4))
Loop

You can also instead read all lines and convert them:

Dim companyids() As String = IO.File.ReadAllLines("data.txt")
For i As Integer = 0 To companyids.Length - 1
    companyids(i) = companyids(i).Substring(2, 4)
Next

This can be simplified with VB 2008:

Dim companyids() As String = Array.ConvertAll(IO.File.ReadAllLines("data.txt"), Function(x) x.Substring(2, 4))