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Null reference exception while using try cast on rich text box

Posted on 2013-01-07
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Last Modified: 2013-03-06
I am trying to cast the sender which is menu item to rich text box. but it throws a null reference exception.  Can anyone please point me in the direction where am I doing wrong? Thank you.

Here is the code.

 
 Private Sub mnuItemCopy_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles mnuItemCopy.Click
Dim c As RichTextBox = TryCast(sender, RichTextBox)
        If c.SelectedText <> Nothing Then
            c.Copy()
        End If

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Thanks!
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Question by:developer2012
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4 Comments
 
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Accepted Solution

by:
Guy Hengel [angelIII / a3] earned 1500 total points
ID: 38752640
you have first to check if "c" is nothing also (aka if the TryCast worked):
 Private Sub mnuItemCopy_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles mnuItemCopy.Click
  Dim c As RichTextBox = TryCast(sender, RichTextBox)
  if c <> Nothing Then
        If c.SelectedText <> Nothing Then
            c.Copy()
        End If
  end if

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LVL 75

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by:käµfm³d 👽
ID: 38752659
Can your sender ever be a RTB? It seems like you've got your handler only handling a menu-item selection.
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Author Comment

by:developer2012
ID: 38752713
@ angeIII as you said, the condition fails at line 3 i.e. if c <> Nothing.

@ Kaufmed...Yes. I tried your idea. did not work for me.

Thanks
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LVL 75

Expert Comment

by:käµfm³d 👽
ID: 38752735
I'm not sure what you mean by, "I tried your idea." I'm saying that it doesn't appear--even if you do sort out the syntax, which angelIII has given you--that your logic is going to give you the result you are looking for. sender is the control which generated the event, not (necessarily) the control you are looking to target for some bit of logic.
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