vb.net bug when trying to showdialog - vb.net

Question

when i try to show dialog of one of my forms it displays this error all other forms work perfectly i have tried to copy the code into another form happened the same
here is the error:
A first chance exception of type 'System.InvalidOperationException'
occurred in hyper market system.exe
Additional information: An error occurred creating the form. See
Exception.InnerException for details. The error is: Object reference
not set to an instance of an object.
If there is a handler for this exception, the program may be safely continued.
here is all my code
Public Class farm
Dim inifile As New IniFile(myfiles & "\system.ini")
Dim myfiles As String = My.Computer.FileSystem.SpecialDirectories.MyDocuments & "\HMsystem"
Private Sub Form2_Load(sender As Object, e As EventArgs) Handles MyBase.Load
End Sub
Private Sub TextBox1_TextChanged(sender As Object, e As EventArgs) Handles TextBox1.TextChanged
End Sub
Dim Count As Integer = 0
Dim total As Long = 0
Dim productnum As String = TextBox1.Text
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim productnum As String = TextBox1.Text
Dim num As String = TextBox2.Text
Dim itemname As String = inifile.GetString("productname", productnum, "غير موجود")
Dim price As String = inifile.GetString("productprice", productnum, "غير موجود")
ListView1.Items.Add(productnum)
ListView1.Items(Count).SubItems.Add(itemname)
ListView1.Items(Count).SubItems.Add(num)
ListView1.Items(Count).SubItems.Add(price)
total += price
Count += 1
Dim a As String = inifile.GetString("productquan", productnum, "0")
Dim itemquannow As String = inifile.GetString("productquan", productnum, "0")
If itemquannow <= 5 Then
Else
MsgBox("لم يبق الا 5 من هذا المنتج")
End If
inifile.WriteInteger("productquan", productnum, a - num)
MsgBox("تم الاضافة")
End Sub
Private Sub TextBox2_TextChanged(sender As Object, e As EventArgs) Handles TextBox2.TextChanged
End Sub
Private Sub Timer1_Tick(sender As Object, e As EventArgs) Handles Timer1.Tick
Label4.Text = total & " السعر النهائي"
End Sub
Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
ListView1.Clear()
TextBox1.Clear()
TextBox2.Clear()
Count = 0
total = 0
MsgBox("تم الشراء بنجاح")
End Sub
Private Sub Label4_Click(sender As Object, e As EventArgs) Handles Label4.Click
End Sub
Private Sub ListView1_SelectedIndexChanged(sender As Object, e As EventArgs) Handles ListView1.SelectedIndexChanged
End Sub
Private Sub Label3_Click(sender As Object, e As EventArgs) Handles Label3.Click
End Sub
Private Sub Label2_Click(sender As Object, e As EventArgs) Handles Label2.Click
End Sub
Private Sub Label1_Click(sender As Object, e As EventArgs) Handles Label1.Click
End Sub
End Class

Answer 1

When you get an error message like that, i.e. "An error occurred creating the form", it almost always means the same basic issue: you have an event handler that is being raised because of a property value set in the designer and that event handler assumes that the user has made that change after the form has been displayed. For instance, if you set the Text property of a TextBox in the designer then that's going to raise the TextChanged event. If you have handled that event then your event handler is going to be executed during the initialisation of the form, before it has been displayed to the user. If you assume that, for instance, an item is selected in a ComboBox then you're in trouble because there will be no such selection.
As the error message states, look at the InnerException, which will tell you exactly where the original exception was thrown. That will tell you which event handler is the issue and you can then look at the code in that method and determine what would cause an issue if the form had not yet been displayed. If in doubt, update your question with the code of that event handler and tell us where the exception was thrown, which the stack trace will tell you.