error appearing randomly

I have tow forms(form1,form2) and want to show form2 from form1 as dialog form and hide form1 while form2 is shown. It seems easy:

Code:

---

dim frm as form=new form2
Me.Hide
frm.ShowDialog

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BUT, the problem is that form2 takes quite a long time to load cause its filled up with lots of controls, so if i use the above method form1 will hide immediately and leaves the user wondering what has happened to the program. I can think of two solutions:
First: Change the windows(not the application) cursor to 'waitcursor' to show the user that something is happening (I really dont know how ;) ).

Second: Hide form1 when form2 load is finished. In order to do this i put the following code in the from2_load sub:

Code:

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Private Sub from2_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
...
    Me.ParentForm.ActiveForm.Hide()
End Sub

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or as an alternative:

Code:

---

Private Sub from2_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
...
  dim frm as Form=form2.ActiveForm
  frm.Hide()
End Sub

---

Both methods work but they stop RANDOMLY !!! with the error : Object Refrence not set to an instance .....

Whats wrong with it? and if it is totaly wrong why it does not make error every time?

I tried this , I worked fine.

VB Code:

Private Sub Button1_Click(ByVal sender As System.Object, _
    ByVal e As System.EventArgs) Handles Button1.Click
        Dim frm2 As New Form2()
        Me.Hide()
        frm2.Show()
    End Sub

Add an argument to the constructor of the dialog form, something like this....

Code:

---

    Dim frmMain As Form
    Public Sub New(ByVal frm As Form)
        MyBase.New()

        frmMain = frm
        'This call is required by the Windows Form Designer.
        InitializeComponent()
        'Add any initialization after the InitializeComponent() call

    End Sub

---

Send the Mainform to the constructor when showing the form....

Code:

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Dim frm As New Form2(Me)
frm.ShowDialog()

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Then hide the mainform as the last you do in the load event of the dialog.

Code:

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frmMain.Hide()

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I agree with Athley but you can use the Owner property of the form instead of making your own. Here is how I'd do it:

VB Code:

'FORM2 CODE
    Private Sub Form2_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        'this will help since the app still kind of stalls while loading
        Me.Cursor = Cursors.WaitCursor
    End Sub
 
    Private Sub Form2_Activated(ByVal sender As Object, ByVal e As System.EventArgs) Handles MyBase.Activated
        Static AlreadyRan As Boolean
        'make sure it only fires once
        If Not AlreadyRan Then
            Me.Owner.Hide()
            Me.Cursor = Cursors.Default
            AlreadyRan=True
        End If
    End Sub
 
    Private Sub Form2_Closing(ByVal sender As Object, ByVal e As System.ComponentModel.CancelEventArgs) Handles MyBase.Closing
        'bring back old form
        Me.Owner.Show()
    End Sub
 
'FORM1 CODE
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        'show busy
        Me.Cursor = Cursors.WaitCursor
        Dim frm As New Form2()
        'pass me as the owner
        frm.ShowDialog(Me)
        'remove busy
        'note cursor for this form is not shown while the form is hidden
        Me.Cursor = Cursors.Default
    End Sub

Thank you all :)