[RESOLVED] Making Arrays larger

[StudNewf]

For this question I am using VB.NET 2003.
I know to make an array larger you use the ReDim Preserve "array" command, but I was wondering how to determine if my original array is too small.
If I make an array 50 "blocks" long, and I am reading from a file that has 55 lines, then how do I know that the array is too small and therefore should make it 100 blocks long, etc.
Thanks

[jmcilhinney]

The following code doubles the length of the array each time, which is what a collection does with its Capacity. You may choose to grow the array by a fixed amount each time instead.

Dim arr(50 - 1) As String
        Dim sr As New IO.StreamReader("C:\MyFile.txt")
        Dim linesRead As Integer = 0
 
        Do Until sr.Peek() = -1
            If linesRead = arr.Length Then
                'We have filled the array so enlarge it.
                ReDim Preserve arr(arr.Length * 2 - 1)
            End If
 
            arr(linesRead) = sr.ReadLine()
        Loop
 
        'Remove unused elements.
        ReDim Preserve arr(linesRead - 1)
 
        sr.Close()

You might also look at using a Specialized.StringCollection instead, depending on the circumstances. It is a collection and thus handles the growing and shrinking automatically.

[jcis]

Dim MyArray(55) As String
        Dim tr As StreamReader = New StreamReader("c:\MyFile.txt")
        Dim intLines As Integer = UBound(Split(tr.ReadToEnd(), vbNewLine)) + 1
 
        If intLines > UBound(MyArray) Then
            ReDim Preserve MyArray(intLines)
        End If
 
        tr.Close()

[StudNewf]

Thats great! Just what I was looking for.
Thanks again

[jmcilhinney]

Dim MyArray(55) As String
        Dim tr As StreamReader = New StreamReader("c:\MyFile.txt")
        Dim intLines As Integer = UBound(Split(tr.ReadToEnd(), vbNewLine)) + 1
 
        If intLines > UBound(MyArray) Then
            ReDim Preserve MyArray(100)
        End If
 
        tr.Close()

If you're going to do it that way then you may as well jsut do this:

Dim myArray As String() = System.Text.RegularExpressions.Regex.Split(myStreamReader.ReadToEnd(), Environment.NewLine)

No need to ever specify the size of the array because you aren't creating it explicilty. You can also use the Split Runtime function but I prefer to avoid Runtime functions. I couldn't really say which is more efficient in this case though.