[RESOLVED] Making Arrays larger

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

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.

VB Code:

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.

VB Code:

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()

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

Quote:

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Originally Posted by jcis

VB Code:

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()

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

VB Code:

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.