Double.Parse for Native language support

Question

I have a value 20,55 which is in German language.
When I change the regional settings to US the value gets displayed as 2055.0 after running this code:

double d = Double.Parse("20,55",CultureInfo.CurrentCUCulture);

Why is that?

Answer 1

In the US, the decimal separator is ., not ,. If you attempt to parse 20,55, it will (apparently) ignore the commas as standard triplet separators (such as in 1,234,567.89), even though there aren't three digits in all of them.

If you want to parse a Euro-style number, you need to parse it with a Euro-style culture setting.

Answer 2

Because in US the , is the thousand separator and it's ignored? In the same way that in Germany (and continental Europe) the . is the thousand separator and it's ignored?

In Germany you write: 1.000,55. In USA you write: 1,000.55 (and there are some schools of thought that remove the , if there is a single digit before. So 1000.55 and 11,000.55).

Now, if you want to be sure your program is using the de-DE culture, pass as a parameter everywhere

CurrentCulture culture = new CultureInfo("de-DE");

double d = double.Parse("20,55", culture);

Answer 3

It's because the US decimal separator is the . and not the ,.

If you want to avoid that problem no matter the regional settings of the user, you could write a extension method:

public static String ToRegionalNumber(this String str) {
    String regionalNb = str.Replace(",", NumberFormatInfo.CurrentInfo.NumberDecimalSeparator);
    regionalNb = regionalNb .Replace(".", NumberFormatInfo.CurrentInfo.NumberDecimalSeparator);
    return regionalNb ;
}

And call this method when working with your number:

double d = Double.Parse("20,55".ToRegionalNumber());