I just started learning Visual Basic a few days ago and have played with this for an hour. If I use line 113 (about ten lines from bottom), I get the
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error. If I replace "textbox1.text" with "fubar", it still gives the error.object reference not set to an instance of an object
VB.NET:
[size=2][color=#0000ff]Imports[/color][/size][size=2] System.Text
[/size][size=2][color=#0000ff]Imports[/color][/size][size=2] System.IO
[/size][size=2][color=#0000ff]Imports[/color][/size][size=2] System.Net
[/size][size=2][color=#0000ff]Public[/color][/size][size=2] [/size][size=2][color=#0000ff]Class[/color][/size][size=2] Form_addremovelist
[/size][size=2][color=#0000ff]Inherits[/color][/size][size=2] System.Windows.Forms.Form
#[/size][size=2][color=#0000ff]Region[/color][/size][size=2] " Windows Form Designer generated code "
[/size][size=2][color=#0000ff]Public[/color][/size][size=2] [/size][size=2][color=#0000ff]Sub[/color][/size][size=2] [/size][size=2][color=#0000ff]New[/color][/size][size=2]()
[/size][size=2][color=#0000ff]MyBase[/color][/size][size=2].New()
[/size][size=2][color=#008000]'This call is required by the Windows Form Designer.
[/color][/size][size=2]InitializeComponent()
[/size][size=2][color=#008000]'Add any initialization after the InitializeComponent() call
[/color][/size][size=2][/size][size=2][color=#0000ff]End[/color][/size][size=2] [/size][size=2][color=#0000ff]Sub
[/color][/size][size=2][/size][size=2][color=#008000]'Form overrides dispose to clean up the component list.
[/color][/size][size=2][/size][size=2][color=#0000ff]Protected[/color][/size][size=2] [/size][size=2][color=#0000ff]Overloads[/color][/size][size=2] [/size][size=2][color=#0000ff]Overrides[/color][/size][size=2] [/size][size=2][color=#0000ff]Sub[/color][/size][size=2] Dispose([/size][size=2][color=#0000ff]ByVal[/color][/size][size=2] disposing [/size][size=2][color=#0000ff]As[/color][/size][size=2] [/size][size=2][color=#0000ff]Boolean[/color][/size][size=2])
[/size][size=2][color=#0000ff]If[/color][/size][size=2] disposing [/size][size=2][color=#0000ff]Then
[/color][/size][size=2][/size][size=2][color=#0000ff]If[/color][/size][size=2] [/size][size=2][color=#0000ff]Not[/color][/size][size=2] (components [/size][size=2][color=#0000ff]Is[/color][/size][size=2] [/size][size=2][color=#0000ff]Nothing[/color][/size][size=2]) [/size][size=2][color=#0000ff]Then
[/color][/size][size=2]components.Dispose()
[/size][size=2][color=#0000ff]End[/color][/size][size=2] [/size][size=2][color=#0000ff]If
[/color][/size][size=2][/size][size=2][color=#0000ff]End[/color][/size][size=2] [/size][size=2][color=#0000ff]If
[/color][/size][size=2][/size][size=2][color=#0000ff]MyBase[/color][/size][size=2].Dispose(disposing)
[/size][size=2][color=#0000ff]End[/color][/size][size=2] [/size][size=2][color=#0000ff]Sub
[/color][/size][size=2][/size][size=2][color=#008000]'Required by the Windows Form Designer
[/color][/size][size=2][/size][size=2][color=#0000ff]Private[/color][/size][size=2] components [/size][size=2][color=#0000ff]As[/color][/size][size=2] System.ComponentModel.IContainer
[/size][size=2][color=#008000]'NOTE: The following procedure is required by the Windows Form Designer
[/color][/size][size=2][/size][size=2][color=#008000]'It can be modified using the Windows Form Designer.
[/color][/size][size=2][/size][size=2][color=#008000]'Do not modify it using the code editor.
[/color][/size][size=2][/size][size=2][color=#0000ff]Friend[/color][/size][size=2] [/size][size=2][color=#0000ff]WithEvents[/color][/size][size=2] Button2 [/size][size=2][color=#0000ff]As[/color][/size][size=2] System.Windows.Forms.Button
[/size][size=2][color=#0000ff]Friend[/color][/size][size=2] [/size][size=2][color=#0000ff]WithEvents[/color][/size][size=2] ListBox1 [/size][size=2][color=#0000ff]As[/color][/size][size=2] System.Windows.Forms.ListBox
[/size][size=2][color=#0000ff]Friend[/color][/size][size=2] [/size][size=2][color=#0000ff]WithEvents[/color][/size][size=2] Button1 [/size][size=2][color=#0000ff]As[/color][/size][size=2] System.Windows.Forms.Button
[/size][size=2][color=#0000ff]Friend[/color][/size][size=2] [/size][size=2][color=#0000ff]WithEvents[/color][/size][size=2] TextBox1 [/size][size=2][color=#0000ff]As[/color][/size][size=2] System.Windows.Forms.TextBox
<System.Diagnostics.DebuggerStepThrough()> [/size][size=2][color=#0000ff]Private[/color][/size][size=2] [/size][size=2][color=#0000ff]Sub[/color][/size][size=2] InitializeComponent()
[/size][size=2][color=#0000ff]Me[/color][/size][size=2].Button2 = [/size][size=2][color=#0000ff]New[/color][/size][size=2] System.Windows.Forms.Button
[/size][size=2][color=#0000ff]Me[/color][/size][size=2].ListBox1 = [/size][size=2][color=#0000ff]New[/color][/size][size=2] System.Windows.Forms.ListBox
[/size][size=2][color=#0000ff]Me[/color][/size][size=2].Button1 = [/size][size=2][color=#0000ff]New[/color][/size][size=2] System.Windows.Forms.Button
[/size][size=2][color=#0000ff]Me[/color][/size][size=2].TextBox1 = [/size][size=2][color=#0000ff]New[/color][/size][size=2] System.Windows.Forms.TextBox
[/size][size=2][color=#0000ff]Me[/color][/size][size=2].SuspendLayout()
[/size][size=2][color=#008000]'
[/color][/size][size=2][/size][size=2][color=#008000]'Button2
[/color][/size][size=2][/size][size=2][color=#008000]'
[/color][/size][size=2][/size][size=2][color=#0000ff]Me[/color][/size][size=2].Button2.Location = [/size][size=2][color=#0000ff]New[/color][/size][size=2] System.Drawing.Point(56, 336)
[/size][size=2][color=#0000ff]Me[/color][/size][size=2].Button2.Name = "Button2"
[/size][size=2][color=#0000ff]Me[/color][/size][size=2].Button2.Size = [/size][size=2][color=#0000ff]New[/color][/size][size=2] System.Drawing.Size(112, 24)
[/size][size=2][color=#0000ff]Me[/color][/size][size=2].Button2.TabIndex = 5
[/size][size=2][color=#0000ff]Me[/color][/size][size=2].Button2.Text = "Remove Selected"
[/size][size=2][color=#008000]'
[/color][/size][size=2][/size][size=2][color=#008000]'ListBox1
[/color][/size][size=2][/size][size=2][color=#008000]'
[/color][/size][size=2][/size][size=2][color=#0000ff]Me[/color][/size][size=2].ListBox1.Location = [/size][size=2][color=#0000ff]New[/color][/size][size=2] System.Drawing.Point(8, 80)
[/size][size=2][color=#0000ff]Me[/color][/size][size=2].ListBox1.Name = "ListBox1"
[/size][size=2][color=#0000ff]Me[/color][/size][size=2].ListBox1.SelectionMode = System.Windows.Forms.SelectionMode.MultiExtended
[/size][size=2][color=#0000ff]Me[/color][/size][size=2].ListBox1.Size = [/size][size=2][color=#0000ff]New[/color][/size][size=2] System.Drawing.Size(216, 251)
[/size][size=2][color=#0000ff]Me[/color][/size][size=2].ListBox1.TabIndex = 6
[/size][size=2][color=#008000]'
[/color][/size][size=2][/size][size=2][color=#008000]'Button1
[/color][/size][size=2][/size][size=2][color=#008000]'
[/color][/size][size=2][/size][size=2][color=#0000ff]Me[/color][/size][size=2].Button1.Location = [/size][size=2][color=#0000ff]New[/color][/size][size=2] System.Drawing.Point(80, 48)
[/size][size=2][color=#0000ff]Me[/color][/size][size=2].Button1.Name = "Button1"
[/size][size=2][color=#0000ff]Me[/color][/size][size=2].Button1.Size = [/size][size=2][color=#0000ff]New[/color][/size][size=2] System.Drawing.Size(72, 24)
[/size][size=2][color=#0000ff]Me[/color][/size][size=2].Button1.TabIndex = 7
[/size][size=2][color=#0000ff]Me[/color][/size][size=2].Button1.Text = "Add"
[/size][size=2][color=#008000]'
[/color][/size][size=2][/size][size=2][color=#008000]'TextBox1
[/color][/size][size=2][/size][size=2][color=#008000]'
[/color][/size][size=2][/size][size=2][color=#0000ff]Me[/color][/size][size=2].TextBox1.Location = [/size][size=2][color=#0000ff]New[/color][/size][size=2] System.Drawing.Point(48, 24)
[/size][size=2][color=#0000ff]Me[/color][/size][size=2].TextBox1.Name = "TextBox1"
[/size][size=2][color=#0000ff]Me[/color][/size][size=2].TextBox1.Size = [/size][size=2][color=#0000ff]New[/color][/size][size=2] System.Drawing.Size(144, 20)
[/size][size=2][color=#0000ff]Me[/color][/size][size=2].TextBox1.TabIndex = 8
[/size][size=2][color=#0000ff]Me[/color][/size][size=2].TextBox1.Text = "Type Symbol to Add Here"
[/size][size=2][color=#008000]'
[/color][/size][size=2][/size][size=2][color=#008000]'Form_addremovelist
[/color][/size][size=2][/size][size=2][color=#008000]'
[/color][/size][size=2][/size][size=2][color=#0000ff]Me[/color][/size][size=2].AutoScaleBaseSize = [/size][size=2][color=#0000ff]New[/color][/size][size=2] System.Drawing.Size(5, 13)
[/size][size=2][color=#0000ff]Me[/color][/size][size=2].ClientSize = [/size][size=2][color=#0000ff]New[/color][/size][size=2] System.Drawing.Size(232, 373)
[/size][size=2][color=#0000ff]Me[/color][/size][size=2].Controls.Add([/size][size=2][color=#0000ff]Me[/color][/size][size=2].TextBox1)
[/size][size=2][color=#0000ff]Me[/color][/size][size=2].Controls.Add([/size][size=2][color=#0000ff]Me[/color][/size][size=2].Button1)
[/size][size=2][color=#0000ff]Me[/color][/size][size=2].Controls.Add([/size][size=2][color=#0000ff]Me[/color][/size][size=2].ListBox1)
[/size][size=2][color=#0000ff]Me[/color][/size][size=2].Controls.Add([/size][size=2][color=#0000ff]Me[/color][/size][size=2].Button2)
[/size][size=2][color=#0000ff]Me[/color][/size][size=2].Name = "Form_addremovelist"
[/size][size=2][color=#0000ff]Me[/color][/size][size=2].Text = "Form_Infinity"
[/size][size=2][color=#0000ff]Me[/color][/size][size=2].ResumeLayout([/size][size=2][color=#0000ff]False[/color][/size][size=2])
[/size][size=2][color=#0000ff]End[/color][/size][size=2] [/size][size=2][color=#0000ff]Sub
[/color][/size][size=2]#[/size][size=2][color=#0000ff]End[/color][/size][size=2] [/size][size=2][color=#0000ff]Region
[/color][/size][size=2][/size][size=2][color=#0000ff]Public[/color][/size][size=2] symbols [/size][size=2][color=#0000ff]As[/color][/size][size=2] [/size][size=2][color=#0000ff]New[/color][/size][size=2] ArrayList
[/size][size=2][color=#0000ff]Private[/color][/size][size=2] [/size][size=2][color=#0000ff]Sub[/color][/size][size=2] Form_addremovelist_Load([/size][size=2][color=#0000ff]ByVal[/color][/size][size=2] sender [/size][size=2][color=#0000ff]As[/color][/size][size=2] System.Object, [/size][size=2][color=#0000ff]ByVal[/color][/size][size=2] e [/size][size=2][color=#0000ff]As[/color][/size][size=2] System.EventArgs) [/size][size=2][color=#0000ff]Handles[/color][/size][size=2] [/size][size=2][color=#0000ff]MyBase[/color][/size][size=2].Load
symbols = LoadSymbolList()
ListBox1.DataSource = symbols
[/size][size=2][color=#0000ff]End[/color][/size][size=2] [/size][size=2][color=#0000ff]Sub
[/color][/size][size=2][/size][size=2][color=#0000ff]Private[/color][/size][size=2] [/size][size=2][color=#0000ff]Sub[/color][/size][size=2] Button2_Click([/size][size=2][color=#0000ff]ByVal[/color][/size][size=2] sender [/size][size=2][color=#0000ff]As[/color][/size][size=2] System.Object, [/size][size=2][color=#0000ff]ByVal[/color][/size][size=2] e [/size][size=2][color=#0000ff]As[/color][/size][size=2] System.EventArgs) [/size][size=2][color=#0000ff]Handles[/color][/size][size=2] Button2.Click
[/size][size=2][color=#0000ff]End[/color][/size][size=2] [/size][size=2][color=#0000ff]Sub
[/color][/size][size=2][/size][size=2][color=#0000ff]Private[/color][/size][size=2] [/size][size=2][color=#0000ff]Sub[/color][/size][size=2] ListBox1_SelectedIndexChanged([/size][size=2][color=#0000ff]ByVal[/color][/size][size=2] sender [/size][size=2][color=#0000ff]As[/color][/size][size=2] System.Object, [/size][size=2][color=#0000ff]ByVal[/color][/size][size=2] e [/size][size=2][color=#0000ff]As[/color][/size][size=2] System.EventArgs) [/size][size=2][color=#0000ff]Handles[/color][/size][size=2] ListBox1.SelectedIndexChanged
[/size][size=2][color=#0000ff]End[/color][/size][size=2] [/size][size=2][color=#0000ff]Sub
[/color][/size][size=2][/size][size=2][color=#0000ff]Private[/color][/size][size=2] [/size][size=2][color=#0000ff]Sub[/color][/size][size=2] Button1_Click([/size][size=2][color=#0000ff]ByVal[/color][/size][size=2] sender [/size][size=2][color=#0000ff]As[/color][/size][size=2] System.Object, [/size][size=2][color=#0000ff]ByVal[/color][/size][size=2] e [/size][size=2][color=#0000ff]As[/color][/size][size=2] System.EventArgs) [/size][size=2][color=#0000ff]Handles[/color][/size][size=2] Button1.Click
[/size][size=2][color=#0000ff]If[/color][/size][size=2] PingSymbol(TextBox1.Text) [/size][size=2][color=#0000ff]Then
[/color][/size][size=2][/size][size=2][color=#0000ff]Dim[/color][/size][size=2] symbols2 [/size][size=2][color=#0000ff]As[/color][/size][size=2] ArrayList = symbols[/size]
[size=2]'''''''''''''''''''''''''''''''''''''
symbols2.Add([/size][size=2][color=#0000ff]Me[/color][/size][size=2].TextBox1.Text)[/size]
[size=2]'''''''''''''''''''''''''''''''''''''''
ListBox1.DataSource = symbols2
[/size][size=2][color=#0000ff]Else
[/color][/size][size=2]MsgBox("Not a valid Symbol")
[/size][size=2][color=#0000ff]End[/color][/size][size=2] [/size][size=2][color=#0000ff]If
[/color][/size][size=2][/size][size=2][color=#0000ff]End[/color][/size][size=2] [/size][size=2][color=#0000ff]Sub
[/color][/size][size=2][/size][size=2][color=#0000ff]Private[/color][/size][size=2] [/size][size=2][color=#0000ff]Sub[/color][/size][size=2] TextBox1_TextChanged([/size][size=2][color=#0000ff]ByVal[/color][/size][size=2] sender [/size][size=2][color=#0000ff]As[/color][/size][size=2] System.Object, [/size][size=2][color=#0000ff]ByVal[/color][/size][size=2] e [/size][size=2][color=#0000ff]As[/color][/size][size=2] System.EventArgs) [/size][size=2][color=#0000ff]Handles[/color][/size][size=2] TextBox1.TextChanged
[/size][size=2][color=#0000ff]End[/color][/size][size=2] [/size][size=2][color=#0000ff]Sub
End[/color][/size][size=2] [/size][size=2][color=#0000ff]Class
[/color][/size]
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