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Prevent non-numeric input

Posted on 2006-07-11
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Last Modified: 2012-06-27
I recall in VB6 that I could basically use the keydown/keypress event to test for the appropriate invalid characters and then just cancel the input (textbox).

What's the proper way for accomplishing this in VB.Net?
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Question by:sirbounty
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bruintje earned 75 total points
ID: 17085615
Hi sirbounty,
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probably the same you can use the keypress like

Private Sub TextBox1_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox1.KeyPress
  If (IsNumeric(e.KeyChar) = False) Then e.Handled = True
End Sub

there is a masked textbox in vb 2005 but its limited to the mask you set [thats the purpose of course ;)]

----------
bruintje
share what you know, learn what you don't
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by:sirbounty
ID: 17085636
Yeah - I've got 2005 at work, but doing this in 2003. :(

Okay, so this will be currency data, can I allow for a decimal as well?
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LVL 67

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by:sirbounty
ID: 17085655
Incidentally, I found this on another forum...not too bad..
Private Sub NumericKeyPress(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox1.KeyPress
Dim tb As TextBox = sender
        If Not (Char.IsDigit(e.KeyChar) Or Char.IsControl(e.KeyChar) Or (e.KeyChar = "." And tb.Text.IndexOf(".") < 0)) Then
            e.Handled = True
        End If
        If (tb.SelectionStart > tb.Text.Length - 2 And tb.Text.IndexOf(".") >= 0 And tb.Text.IndexOf(".") + 3 = tb.Text.Length) Then
            e.Handled = True
        End If
        If e.Handled = False And tb.Text.Length = 0 Then
            tb.Text = "$" + e.KeyChar
            e.Handled = True
            tb.SelectionStart = 2
        End If
End Sub
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Expert Comment

by:bruintje
ID: 17085705
well, then you solved your own question :-)
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