protected override void OnKeyPress(KeyPressEventArgs e)
{
    base.OnKeyPress(e);

    var keyInput = e.KeyChar.ToString();
    var nfi = System.Globalization.CultureInfo.CurrentCulture.NumberFormat;

    if (Char.IsDigit(e.KeyChar))
    {
        // Digits are acceptable
    }
    else if (keyInput.Equals(nfi.NumberDecimalSeparator) && Text.IndexOf(nfi.NumberDecimalSeparator) == -1 && !integer)
    {
        // Decimal separator is allowed only once for non-integers
    }
    else if (keyInput.Equals(nfi.NegativeSign) && SelectionStart == 0 && Text.IndexOf(nfi.NegativeSign) == -1 && !positive)
    {
        // Negative sign allow only once at the beginning
    }
    else if (e.KeyChar == '\b')
    {
        // Backspace key is allowed
    }
    else if (ModifierKeys == Keys.Control && e.KeyChar == 22)
    {
        // Paste is allowed
    }
    else
    {
        // Skip the invalid key
        e.Handled = true;
    }
}