Question

There a way to use e.Cancel () on a keyup event?

I’m trying to validate a textbox with a Regex and I need to cancel the event if it no meets the Regex expression, or delete the key pressed to meet so that the expression

For Example:

Dim rex As Regex = New Regex("^[0-9]{0,9}(\.[0-9]{0,2})?$")
Private Sub prices_KeyUp(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles Textbox1.KeyUp,

        Dim TxtB As TextBox = CType(sender, TextBox)

        If (rex.IsMatch(TxtB.Text) = False ) Then
            e.cancel = true
        End If

    End Sub

ERROR: ‘cancel’ is not a member of ‘System.Windows.Forms.KeyEventArgs’.

Answer 1

Try

If (rex.IsMatch(TxtB.Text) = False) Then
  e.SuppressKeyPress = True
End If

From MSDN:

You can assign true to this property in an event handler such as KeyDown in order to prevent user input.

Setting SuppressKeyPress to true also sets Handled to true.

It’s unclear what you are trying to cancel though, since you are reading the TextBox.Text value. KeyDown is usually the preferred event to intercept the keystroke.

If you are trying to validate the entire string, the Validating event might be more appropriate. With TextBox controls, you will always have the danger of someone pasting clipboard text into the control, which could bypass key events.