File Reading Error?

[Infexious]

Hello!

I have the following code under my button:

    Private Sub SearchButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles SearchButton.Click
        MsgBox(SearchBox.Text())
        If (File.Exists("Database.bin")) And (SearchBox.Text() <> Nothing) Then
            Dim ioFile As New StreamReader("Database.bin")
            Dim ioLine As String ' Holds 1 Line at a Time
            Dim ioLines As String ' Holds Whole File
            ioLines = ""
            Do
                ioLine = ioFile.ReadLine()
                If (ioLine.IndexOf(SearchBox.Text()) <> -1) Then
                    If (ioLine <> Nothing) Then
                        DisplayBox.Items.Add(ioLine)
                    End If
                End If
                ioLines = ioLines & vbCrLf & ioLine
            Loop Until ioLine Is Nothing
            'MsgBox(ioLines)
        Else
            MsgBox("Database.bin is missing! Please re-download the program.")
        End If
    End Sub

It is supposed to open "Database.bin", search the file for whatever the user types into SearchBox (a text box), and add to DisplayBox (a list box) every line of that file that contains the string the user searched. However, it always returns this exception:

System.NullReferenceException was unhandled
  Message=Object reference not set to an instance of an object.
  Source=Universal Handbook
  StackTrace:
       at Universal_Handbook.MainWindow.SearchButton_Click(Object sender, EventArgs e) in C:\Users\Cecil\documents\visual studio 2010\Projects\Universal Handbook\Universal Handbook\Form1.vb:line 21
       at System.Windows.Forms.Control.OnClick(EventArgs e)
       at System.Windows.Forms.Button.OnClick(EventArgs e)
       at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
       at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
       at System.Windows.Forms.Control.WndProc(Message& m)
       at System.Windows.Forms.ButtonBase.WndProc(Message& m)
       at System.Windows.Forms.Button.WndProc(Message& m)
       at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
       at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
       at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
       at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
       at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.Run(ApplicationContext context)
       at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.OnRun()
       at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.DoApplicationModel()
       at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.Run(String[] commandLine)
       at Universal_Handbook.My.MyApplication.Main(String[] Args) in 17d14f5c-a337-4978-8281-53493378c1071.vb:line 81
       at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
       at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
       at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
       at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       at System.Threading.ThreadHelper.ThreadStart()
  InnerException:

Could someone please inform me of what is wrong and help me correct it?

Here is Database.bin:

1010000    Long Brown Beard    
1010001    Goatee    
1010002    Ninja Mask for Men    
1010003    5 O'Clock Shadow    
1010004    General's Mustache (1)    
1010005    General's Mustache (2)    
1010006    Yakuza Scar    
1011000    Ninja Mask for Women    
1011001    SF Ninja Mask    
1011002    Heart    
1011003    Freckles    
1012000    Battle Scar    
1012001    Bindi    
1012002    Leather Mask    
1012003    Blush    
1012004    Disguise    
1012005    Bruise    
1012006    Rose    
1012007    Santa Beard    
1012008    Censor    
1012009    Kiss Mark    
1012010    Hinomaru

Help is greatly appreciated!

[jmcilhinney]

You have your Until clause at the end of the loop, which means that a line will already have been read and processed before you make that check, by which time it's too late. If you want to read a file line by line using a StreamReader then do so like this:

Using reader As New IO.StreamReader("file path here")
    Do Until reader.EndOfStream
        Dim line = reader.ReadLine()
 
        'Use line here.
    Loop
End Using

If you want the items in a ListBox and the entire text elsewhere though, there's an easier way:

Dim lines As String() = IO.File.ReadAllLines("file path here")
 
Me.ListBox1.DataSource = lines
 
Dim content As String = String.Join(Environment.NewLine, lines)

Finally, it doesn't really make sense to use a ".bin" extension, which implies binary data, to store text. A ".dat" extension, implying data, would be more appropriate.

[Infexious]

Oh okay. I see now, thanks. I am pretty new to VB and I'm used to C++. And by the way, I was just using ".bin" to try and "hide" the file from any users of the program, though I guess a ".dat" would be more appropriate.

[marniel647]

You have your Until clause at the end of the loop, which means that a line will already have been read and processed before you make that check, by which time it's too late. If you want to read a file line by line using a StreamReader then do so like this:

Using reader As New IO.StreamReader("file path here")
    Do Until reader.EndOfStream
        Dim line = reader.ReadLine()
 
        'Use line here.
    Loop
End Using

If you want the items in a ListBox and the entire text elsewhere though, there's an easier way:

Dim lines As String() = IO.File.ReadAllLines("file path here")
 
Me.ListBox1.DataSource = lines
 
Dim content As String = String.Join(Environment.NewLine, lines)

Finally, it doesn't really make sense to use a ".bin" extension, which implies binary data, to store text. A ".dat" extension, implying data, would be more appropriate.

thanks for this JM..... i learn now how to read a file..