[RESOLVED] Control.Validated

[Seraph]

Is there anyway to check if a Control has been validated yet?
I have some code that I want to run when the Selected of a TabControl fires off.
The thing is, that I have TabPages added to the TabControl at the beginning of runtime, which then triggers the Selected event before the control is completely existent, which means the Sub I have that also happens to reference the control during that event errors out because there is technically not an instance of the control completely finished building so it says I don't have a correct reference set to that object.

So basically, I want to be able to check in the Sub if the control has been Validated, or maybe even created or whatever is going on.

[jmcilhinney]

How do you usually check whether an object exists?

If myObj IsNot Nothing Then
    'Use myObj here.
End If

[Seraph]

Here's my code:

If My.Settings.TabOrder IsNot Nothing AndAlso My.Settings.TabOrder.Count > 0 Then
            'Check if there is a tab order stored
            'Removes pages from tabcontrol, stores them and inserts tabs into new order
            Dim pages As New Collection(Of cTabPage)
            pages.Add(CType(tabPage1, cTabPage))
            pages.Add(CType(tabPage2, cTabPage))
            pages.Add(CType(tabPage3, cTabPage))
            pages.Add(CType(tabPage4, cTabPage))
            pages.Add(CType(tabPage5, cTabPage))
            padControl.TabPages.Clear()
            For Each o As Object In My.Settings.TabOrder
                Select Case o.ToString
                    Case "tabPage1"
                        padControl.TabPages.Add(pages(0))
                    Case "tabPage2"
                        padControl.TabPages.Add(pages(1))
                    Case "tabPage3"
                        padControl.TabPages.Add(pages(2))
                    Case "tabPage4"
                        padControl.TabPages.Add(pages(3))
                    Case "tabPage5"
                        padControl.TabPages.Add(pages(4))
                End Select
            Next
        End If

Public Sub setTitleBar()
        If padControl IsNot Nothing Then
            With My.Settings
                If .TitleBarDisplayPad = 0 Then
                    Me.Text = "TrayPad"
                ElseIf .TitleBarDisplayPad = 1 And .TitleBarRemoveTrayPad = 0 Then
                    Me.Text = "TrayPad - " & padControl.SelectedTab.Text
                ElseIf .TitleBarRemoveTrayPad = 1 Then
                    Me.Text = padControl.SelectedTab.Text
                End If
            End With
        End If
    End Sub

Private Sub padControl_Selected(ByVal sender As Object, ByVal e As System.Windows.Forms.TabControlEventArgs) Handles padControl.Selected
        setTitleBar()
    End Sub

The first block of code is what is triggering the Selected event for padControl.
The second block of code is the Sub where I have the code I want done.
The third block is pretty obvious.

Because of block 1, block 3 is triggered each time a tab is readded to the padControl.
Even though I enclosed the Sub code with what you suggested, it's still giving me an error.

[jmcilhinney]

Instead of saying something like "errors out", please provide the type of exception and the error message. Is it a NullReferenceException? An InvalidOperationException? Something else? Exactly which line does the error occur on? If we have all the relevant information in the first place then we don't have to guess or make assumptions.

[Seraph]

"NullReferenceException" on "Me.Text = "TrayPad - " & padControl.SelectedTab.Text"

[jmcilhinney]

It's a NullReferenceException so have you checked which reference is null? You're already testing padControl in code so it's not going to be that, which doesn't leave many options. The only other references are Me, which is obviously not null, and padControl.SelectedTab.

[Seraph]

:/ How can the SelectedTab be null? The Selected event got raised. Doesn't the control have to exist to raise an event on it?

[VBDT]

I think a better way would be to get the selected TobPage text in the Selected event handler of the TabControl and pass it as a parameter to the setTitleBar method. It might be that the selected event happens befor the SelectedTab property of the TabControl is set.

Private Sub TabControl1_Selected(ByVal sender As Object, ByVal e As System.Windows.Forms.TabControlEventArgs) Handles TabControl1.Selected
    Me.setTitleBar(e.TabPage.Text)
End Sub
 
Public Sub setTitleBar(ByVal tabText As String)
    '....
    '....
    '....
End Sub

[Seraph]

hmm..ok i see.
I always think of a control as being a whole thing that has to be complete to exist, but i guess that isn't true. I've looked inside a custom control once and mssed with it, but I don't do it enough to always be thinking of how that all really works. even in a control there is procedural type code, so things have to come before others.
Thanks, that makes more sense. I guess I'll just have to play with it.

[Seraph]

Yup, got it to work that way. Thanks for the help.