Double Regex gives back the wrong number

Question

I made a Regex which filters for double values.

For example one TextBox contains volume and I use this regex for

double ConvertToDouble(String input)
{
    // Matches the first numebr with or without leading minus.
    Match match = Regex.Match(input, "[+-]?\\d*\\.?\\d+");

    if (match.Success)
    { 
        return Double.Parse(match.Value);
    }
    return 0; // Or any other default value.
}

Somehow this returns 0 when I enter 0,5 into the TextBox.

Answer 1

我建议使用double.TryParse并完全摆脱正则表达式：

// static : we don't use "this" in the method
static double ConvertToDouble(String input)
{
    // if we can parse input...
    if (double.TryParse(input, out double result))
        return result; // ...return the result of the parsing
    else
        return 0.0;    // otherwise 0.0 or any default value
}