VB.net Object Array throwing an exception

Question

I am getting an exception when running the following code.

Public Function getSongs() As Song()
   ' Dim dir As New DirectoryInfo(Application.ExecutablePath)
     Dim dir As New DirectoryInfo(directory)
     Dim songsInDir() As Song = Nothing
     Dim i As Integer = 0
     For Each file As FileInfo In dir.GetFiles()
        'only read ".mp3" files
        If file.Extension = ".mp3" Then
            songsInDir(i) = New Song(file.Name)
            i = +i
        End If
    Next
    Return songsInDir
End Function

I get an error on line:

songsInDir(i) = New Song(file.Name)

I get an uncaught exception that says:

"Object reference not set to an instance of an object."

The song object has a:

Public Sub new(By Val filename as String)

... sub that sets a variable and retrieves file info (this code works)

Any help would be appreciated!

LarsTech · Accepted Answer · 2012-02-24 23:19:59Z

2

Try using a list:

Public Function getSongs() As Song()
  Dim dir As New DirectoryInfo(directory)
  Dim songsInDir() As New List(of Song)
  For Each file As FileInfo In dir.GetFiles()
    'only read ".mp3" files
    If file.Extension = ".mp3" Then
      songsInDir.Add(New Song(file.Name)
    End If
  Next
  Return songsInDir.ToArray()
End Function

answered Feb 24, 2012 at 23:19

LarsTech

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Comments

JamieSee · Accepted Answer · 2012-02-24 23:30:35Z

0

Your problem is that arrays need a size when they're initialized and setting it to Nothing gives you exactly that. Give the array a size and don't set it to Nothing. Also, there's a much cleaner way to do this.

Public Function getSongs() As Song()
    Dim songFiles As String() = Directory.GetFiles(directory, "*.mp3")
    Dim songsInDir(songFiles.Length) As Song
    Dim i As Integer = 0
    For Each file As String In songFiles
        songsInDir(i) = New Song(Path.GetFileName(file))
        i = +i
    Next
    Return songsInDir
End Function

edited Feb 24, 2012 at 23:30

answered Feb 24, 2012 at 23:22

JamieSee

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Comments

Mohammad Shraim · Accepted Answer · 2012-02-24 23:23:43Z

-1

You should specify the array size

Dim i as Integer = dir.GetFiles().count or dir.FilesCount()

Dim songsInDir(i) As Song = Nothing

or you can use dynamic array

put this line inside your for loop

ReDim Preserve songsInDir(i)

edited Feb 24, 2012 at 23:23

answered Feb 24, 2012 at 23:10

Mohammad Shraim

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3 Comments

Mohammad Shraim Over a year ago

I don't know why someone VoteDown for my answer? While its correct!!

John Koerner Over a year ago

ReDim Preserve is not a good method to use as it wastes resources everytime you reallocate the array.

Mohammad Shraim Over a year ago

It was alternative solution,, i have provide two for him.!!

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