object reference error

[phpman]

I have this bit of code

Private Sub SpellChkMenuItem_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles SpellChkMenuItem.Click
        Dim activeRichTextBox = TryCast(Me.ActiveControl, RichTextBox)
        'clsFS.CheckSpelling(activeRichTextBox)
        'clsFS.SpellAndGrammarCheck(activeRichTextBox)
        If Len(activeRichTextBox.Text) > 0 Then
            SpellChecker.Text = activeRichTextBox.Text
            SpellChecker.SpellCheck()
        Else
            MsgBox("Text box is empty")
            End If
    End Sub

When I am in the rtb and click on spell check button it tells me the error

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

On this line

SpellChecker.Text = activeRichTextBox.Text

But it is suppose to be getting the focused rtb correct? So why is it not referenced

[kareninstructor]

Try the following

    Private Sub demo()
        Dim activeRichTextBox As New RichTextBox
        If TypeOf Me.ActiveControl Is RichTextBox Then
            activeRichTextBox = DirectCast(Me.ActiveControl, RichTextBox)
            If activeRichTextBox.Text.Length > 0 Then
                ' assumes SpellChecker exists already and has been properly created
                SpellChecker.Text = activeRichTextBox.Text
                SpellChecker.SpellCheck()
            Else
                MsgBox("Text box is empty")
            End If
        Else
            Console.Write("Nope")
        End If
    End Sub

[stanav]

Doesn't the menuitem become the activecontrol when you click on it? And obviously a menuitem cannot be cast to a richtextbox, so TryCast(me.activecontrol, richtextbox) returns Nothing therefore you get a null reference exception when you try to treat Nothing as a richtextbox.

[phpman]

So would it be better if I had a right click menu on the RTB?

[techgnome]

Possibly not... as then the menu would become the active control.
the way I'd deal with it (and admittedly it is far less than ideal) is to create a form level object of type RTB... then as an RTB gets focus (I'm assuming you have more than one) ... set the form-level object equal to the RTB that just got focus... then use the form-level object in your code above.

-tg

[kareninstructor]

Doesn't the menuitem become the activecontrol when you click on it? And obviously a menuitem cannot be cast to a richtextbox, so TryCast(me.activecontrol, richtextbox) returns Nothing therefore you get a null reference exception when you try to treat Nothing as a richtextbox.

Yes the menu item becomes the active control but the ContextMenu SourceControl property indicates which control invoked the menu item as shown below.

Private Sub DemoToolStripMenuItem_Click( _
    ByVal sender As System.Object, _
    ByVal e As System.EventArgs) _
    Handles DemoToolStripMenuItem.Click

    If ContextMenuStrip1.SourceControl IsNot Nothing Then
        If TypeOf ContextMenuStrip1.SourceControl Is RichTextBox Then
            Dim activeRichTextBox As New RichTextBox
            activeRichTextBox = DirectCast(ContextMenuStrip1.SourceControl, RichTextBox)
            activeRichTextBox.AppendText("Hello")
        End If
    End If

End Sub

[phpman]

Thanks techgnome, I will give that a shot

And thank Kevin, I will look over that as well.