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

Question

Trying to show other form if textbox's text is correct. When I debug I get an error saying "Object reference not set to an instance of an object". The code is below:

'OK is OK button, MainForm is the form I'm trying to open     

Private Sub OK_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles OK.Click
    Dim pass As String = My.Computer.FileSystem.ReadAllText("password.txt")
    If PasswordTextBox.Text = pass Then
        MainForm.Owner = Me
        Me.Hide()
        '"Object reference not set to an instance of an object" error when debugging on line below
        MainForm.Show()
    End If
End Sub

Where do you declare and initialize `MainForm`? Btw, why do you have a password at all? — Tim Schmelter, Mar 31 '13 at 23:10
@Tim to protect from other people who use my computer a lot. don't wan't them using this program. — user2221877, Mar 31 '13 at 23:12
I don't think you can show a form whose owner is hidden, which is what you're trying to do. Does it work if you remove `Me.Hide()`? — Steven Liekens, Mar 31 '13 at 23:14
@TimSchmelter the path for the text file is longer, I just cut it out because I don't want the world to know where everything is on my computer. — user2221877, Mar 31 '13 at 23:24
You need to create a variable to hold the new instance of your main form. `Dim theFormIWantToShow As New MainForm theFormIWantToShow.Show()` — Jeremy, Apr 01 '13 at 22:04

Jeremy · Answer 1 · 2013-04-01T22:02:48.047

1

You need to create a new instance of the form you want to display. You do this by creating a variable of form T and then showing it.

If you don't create an instance of your form the MainForm.Show() code will be invoking Show() on an null reference.

If PasswordTextBox.Text = pass Then
    Me.Hide()
    Dim theFormIWantToShow As New MainForm
    theFormIWantToShow.Show()
End If

edited Apr 01 '13 at 22:02

answered Apr 01 '13 at 00:59

Jeremy

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

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