Format TextBox only Numerical Data and 2 decimal places, enable backspace

Question

Hi,

I have managed to format a text box to be formatted to two decimal places, and to only accept numbers.

Only problem is i need to allow the backspace so that if someone types something wrong, they can backspace and type the correct number

 

  Private Sub txtCAmount_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles txtCAmount.KeyPress

    'Allow only numberical input plus decimal.
    Dim allowedChars As String = "0123456789."
    If allowedChars.IndexOf(e.KeyChar) = -1 Then
      ' Invalid Character
      e.Handled = True
    End If

  End Sub

  Private Sub TextBox1_Leave(ByVal sender As Object, ByVal e As System.EventArgs) Handles txtCAmount.Leave

    'Format to 2 decimal places.
    txtCAmount.Text = Format(Double.Parse(txtCAmount.Text), "###,###,##0.00")

  End Sub

Can someone tell me how I could modify above to allow the backspace?

Thanks.

 

Answer 1

Will this work?

Dim allowedChars As String = "0123456789." & vbBack
If allowedChars.IndexOf(e.KeyChar) = -1 Then
   ' Invalid Character
   e.Handled = True
End If

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v/r LikeToCode....Mark the best replies as answers.

Answer 2

Perfect.

Answer 3

LikeToCode's method looks like it'll work for you but just an opinion here (and nothing more:)...

I don't even try to do any of that. If the idiot is dumb enough to type "six" instead of "6", then tell him/her it won't work, but I don't prevent them from doing it.

Instead, consider using Double.TryParse which will return a boolean. In other words, if it successfuly converted it to a double, proceed, but if not, clear the text box, put the focus back in it, then pop up a message indicating that their input wasn't valid.

Food for thought

Answer 4

Some of the best number formatting that I know are in this link. Check out in particular, the post by dbasnet:

http://social.msdn.microsoft.com/Forums/en-US/vblanguage/thread/4f84cbd1-4bc1-43af-8fe6-7080c85e02e2

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Only performance counts!

Answer 5

Private Sub TextBox1_KeyPress(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox1.KeyPress

    If Not Char.IsDigit(e.KeyChar) AndAlso Not Char.IsControl(e.KeyChar) AndAlso Not e.KeyChar = "."c Then
      e.Handled = True
    End If

  End Sub

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Asgar

Answer 6

Private Sub TextBox1_KeyPress(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox1.KeyPress



 If Not Char.IsDigit(e.KeyChar) AndAlso Not Char.IsControl(e.KeyChar) AndAlso Not e.KeyChar = "."c Then

  e.Handled = True

 End If



 End Sub

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Asgar

 

Asgar,

Shouldn't there also be an "Else" with "e.Handled=False", or is that not needed?

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Never mind - I see what you're doing now. You're taking care of everything anyone could type on the keyboard so there really IS no "else".

Answer 7

i THINK YOU HAVE GOT IT BUT YOUR SUGGESTION IS THE BEST.

Not allowing a user to type in the textBox is an irritation to  the user.

 

 

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Asgar