Allow only alphanumeric in textbox.

[Prajeesh]

I have a textbox and it need the user not allow to enter any specialcharecters He can enter 1. A-Z                   2. a-z                   3. 0-9                   4. Space. How can I make the KeyDown event to do this?

[Pete OHanlon]

Rather than use KeyDown, try PreviewKeyDown on this instead. More importantly though, are you sure you've thought this through properly? What happens if the user presses the backspace or Delete key? What about the Tab key?

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As Braveheart once said, "You can take our freedom but you'll never take our Hobnobs!" - Martin Hughes.

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[Prajeesh]

What I need is he can't enter any special characters in the textbox.

[Pete OHanlon]

How do you define a special character? You need to think about your requirements a bit more. For instance, what about an apostrophe? If you're masking inputs like this, you wouldn't allow my surname through - and that would seriously annoy me (to the point where I probably wouldn't use your product).

"WPF has many lovers. It's a veritable porn star!" - Josh Smith

As Braveheart once said, "You can take our freedom but you'll never take our Hobnobs!" - Martin Hughes.

My blog | My articles | MoXAML PowerToys | Onyx

[Kschuler]

I like to use the KeyPress event. Here is a sample that allows only alpha characters, numbers, and the control keys like enter, tab, backspace, delete, etc.

Private Sub txtMyTextbox_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles txtMyTextbox.KeyPress
If Char.IsDigit(e.KeyChar) OrElse Char.IsControl(e.KeyChar) OrElse Char.IsLetter(e.KeyChar) Then
e.Handled = False
Else
e.Handled = True
End If
End Sub