Question

I have a little problem with a textbox. I want it to take a price but the problem is that we can enter multiple commas which will make everything not work. I want to limit the number of commas to 1

Here is what I tried:

If ("0123456789,\b".IndexOf(e.KeyChar) = -1) Then
  If e.KeyChar <> Convert.ToChar(Keys.Back) Then
    If (",".IndexOf(e.KeyChar) = -1) And txtPrix.Text.Contains(",") Then
      e.Handled = False
    Else
      e.Handled = True
    End If
  End If

Answer 1

The most reliable would be to use Double.TryParse or Decimal.TryParse:

Dim d = Double.MinValue
If Double.TryParse(txt.Text, d)
    ' it's a number 
Else
    ' it's not a number 
End If