在.NET C＃中解析未知文化的最佳方法是什么？

Question

I'm using XML files to store user data. Files may be saved and loaded from different localisation. Depending on the culture, a double number can be saved as "1.2345" or as "1,2345". The difference is the decimal separator.

Currently I'm using the following code for parsing:

private double StringToDouble(string input)
{
    string decimalPoint = NumberFormatInfo.CurrentInfo.NumberDecimalSeparator;

    if (!input.Contains(decimalPoint))
    {
        input = input.Replace(".", decimalPoint);
        input = input.Replace(",", decimalPoint);
    }

    return double.Parse(input);
}

The code above works well, but obviously it is not the best. Can you offer a better solution?

Answer 1

If you serialize your double to your xml file as a double primitive and not as a string, it will save it with "." so you can parse it with invariant culture.

If it's saved as text, you can try something like this:

double result = double.Parse(input.Replace(",", "."), CultureInfo.InvariantCulture);

Note that you can still have problems with thousands separators in numbers like "1.234.567,89".

Answer 2

Honestly I don't think your current solution is too bad. It isn't elegant, but you are given non-elegant data. As others have suggested, I would see if it is possible to get the XML files in a consistent format, or at least have the XML files saved with a culture info:

<yourRootElement xml:lang="en-US">

That way you won't have to guess.

Barring that, you could also do something like this:

private double StringToDouble(string input)
{
    var last = input.LastIndexOfAny(new[] {',', '.'});
    var separator = last >= 0 ? input[last] : '.';
    var clone = (CultureInfo)CultureInfo.InvariantCulture.Clone();
    clone.NumberFormat.NumberDecimalSeparator = separator.ToString(CultureInfo.InvariantCulture);
    return double.Parse(input, clone);
}

CultureInfo.Clone is expensive, but you can cache culture info based on what the separator is. This also gives you the flexibility to set up different thousands separators, if needed. You would have to assume what the thousands separator is depending on the decimal separator.

Answer 3

I would recommend to save numbers in a fixed fformat, ie with fixed decimal separator. This means that transformation from the user's culture to the culture in which number must be saved should be performed.