Initiating an Dynamic Multidimensional Array in VB.net

Question

I am receiving a "Object reference not set to an instance of an object." Error when trying to populate the fileDetails array. I am new to vb.net and I am lost.

Public Sub FindAllOrphanFiles(ByVal targetDirectory As String)
    Dim fileEntries As String() = Directory.GetFiles(targetDirectory)

    ' Process the list of files found in the directory. 
    Dim files As String
    Dim iCount As Integer = 0
    Dim fileDetails As String(,)
    For Each files In fileEntries
        Dim fileIcon As String
        Dim thisFile As New IO.FileInfo(files)

        Dim fileName As String = thisFile.Name
        Dim fileSize As String = thisFile.Length
        Dim fileDateModified As String = thisFile.LastWriteTime
        Dim fileExtension As String = Path.GetExtension(fileName)
        Dim fileShortPath As String = Replace(Replace(files, uploadFolderPath, ""), fileName, "")
        Dim fileFullPath As String = files
        If fileExtension = ".pdf" Then
            fileIcon = "acrobat"
        Else
            fileIcon = "paint"
        End If

        ' Write to Array
        fileDetails(iCount, 0) = fileIcon
        fileDetails(iCount, 1) = fileName
        fileDetails(iCount, 2) = fileShortPath
        fileDetails(iCount, 3) = fileDateModified
        fileDetails(iCount, 4) = fileSize
        fileDetails(iCount, 5) = fileFullPath

        iCount += 1
    Next files
    Dim subdirectoryEntries As String() = Directory.GetDirectories(targetDirectory)

    ' Recurse into subdirectories of this directory. 
    Dim subdirectory As String
    For Each subdirectory In subdirectoryEntries
        FindAllOrphanFiles(subdirectory)
    Next subdirectory

End Sub 'FindAllOrphanFiles

Any help would be greatly appreciated.

your array is declared but not initialized to any size. Since it is difficult to know ahead of time how big to make them, consider a collection type. possible duplicate of What is a NullReferenceException and how do I fix it? — Ňɏssa Pøngjǣrdenlarp
– Ňɏssa Pøngjǣrdenlarp, Commented Aug 1, 2014 at 18:19
You should really concider using a List(Of ) and store the information properly inside a class. This will reduce a lot of your problem and add redability to your code. — the_lotus
– the_lotus, Commented Aug 1, 2014 at 18:47

Steve · Accepted Answer · 2014-08-01 22:03:00Z

2

Your array is not initialized. If you know the size at some point before your loop, you should initialize it using REDIM:

Dim fileDetails As String(,)
redim fileDetails(fileEntries.Count -1,5)
For Each files In fileEntries
  ....

If you don't know it ahead of time, use Redim Preserve inside you loop:

Dim fileDetails As String(,)
Dim I as int32 = -1
For Each files In fileEntries
    I += 1
    redim preserve fileDetails(i,5)
    ....

answered Aug 1, 2014 at 22:03

Steve

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