Strange problem with the minus(subtract) key

roidy

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Aug 1, 2009, 2:27:50 PM8/1/09

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I have a text box and I need to limit the input to just numbers, backspace
and the minus(subtract) key. I`ve set up a KeyPress event for the text box
and am using the following code:-

Private Sub textbox_KeyPress(ByVal sender As System.Object, _
ByVal e As System.Windows.Forms.KeyPressEventArgs) _
Handles textbox.KeyPress

If Not Char.IsNumber(e.KeyChar) And _
Not e.KeyChar = Chr(Keys.Back) And _
Not e.KeyChar = Chr(Keys.Subtract) Then
e.Handled = True
End If
End Sub

This works perfectly for the number keys and the backspace key but not for
the minus(subtract) key. I can replace Keys.Subtract for any other key on
the keyboard and it works but I can`t get Keys.Subtract to work. Any ideas?

Thanks
Rob

Teemu

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Aug 1, 2009, 4:47:17 PM8/1/09

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"roidy" <r...@nnnnnn.com> kirjoitti viestiss�
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> This works perfectly for the number keys and the backspace key but not for
> the minus(subtract) key. I can replace Keys.Subtract for any other key on
> the keyboard and it works but I can`t get Keys.Subtract to work. Any
> ideas?

Does this work as you expected:

If Not Char.IsNumber(e.KeyChar) AndAlso _
Not e.KeyChar = Chr(Keys.Back) AndAlso _
Not e.KeyChar = "-" Then

e.Handled = True
End If

-Teemu

roidy

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Aug 1, 2009, 4:55:45 PM8/1/09

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That worked perfectly, it never occurred to me to just use "-", seems
strange that Keys.Subtract doesn't work through.

Thanks
Rob

"Teemu" <tsi...@hotmail.com> wrote in message
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Teemu

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Aug 2, 2009, 5:01:47 AM8/2/09

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"roidy" <r...@nnnnnn.com> kirjoitti viestiss�
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> That worked perfectly, it never occurred to me to just use "-", seems
> strange that Keys.Subtract doesn't work through.

I'm not totally sure, but if I remember correctly, these Keys.Subtract,
Keys.Add and others should be used only in KeyDown and KeyUp events to look
up e.KeyCode.

KeyPress event returns just a character and KeyUp and KeyDown events return
a key code for example F-buttons and other special buttons.

-Teemu

roidy

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Aug 2, 2009, 10:39:38 AM8/2/09

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Yep I just tested it and your right, but it seems kind of strange that
Keys.Back and most other keys can be used in a KeyPress event but not
Keys.Subtract. Oh well.

Rob

"Teemu" <tsi...@hotmail.com> wrote in message

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Teemu

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Aug 2, 2009, 12:53:15 PM8/2/09

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"roidy" <r...@nnnnnn.com> kirjoitti viestiss�
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> Yep I just tested it and your right, but it seems kind of strange that
> Keys.Back and most other keys can be used in a KeyPress event but not
> Keys.Subtract. Oh well.

Those Keys enumerations which have same integer as character's ASCII code
(letters, backspace and a few others) will "accidentally" work although it
is much easier to use for example "h" or "&" in KeyPress event.

-Teemu

Armin Zingler

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Aug 2, 2009, 2:49:24 PM8/2/09

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roidy schrieb:

> Yep I just tested it and your right, but it seems kind of strange that
> Keys.Back and most other keys can be used in a KeyPress event but not
> Keys.Subtract. Oh well.

See http://msdn.microsoft.com/en-us/library/ms646267(VS.85).aspx and the
explanation of virtual key codes and character messages.

Armin