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            if (e.KeyChar == '.' || e.KeyChar == ',')
            {
                e.KeyChar = CultureInfo.CurrentCulture.NumberFormat.NumberDecimalSeparator[0];
                e.Handled = tbEingaben.Text.Contains(e.KeyChar);
            }
            else
            {
                e.Handled = !Char.IsNumber(e.KeyChar) && e.KeyChar != (char)Keys.Back;
            }