Is Int32.ToString() culture-specific?

As tested on a random sample of ints, all 352 cultures installed with Windows (CultureTypes.InstalledWin32Cultures) give identical results.

Daniel is right to note a custom culture could use a different prefix for negative numbers, but I doubt anyone has ever used this feature save by accident.

I guess the .NET devs did it to be consistent with float and other types. What else were they expecting?

> int.MaxValue.ToString(CultureInfo.AncientRome)
MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM....

The Operating System allows to change the negative sign for numbers.

Control panel -> 
   Language and regional settings -> 
         Additional settings -> 
             Negative sign

So, current culture could have overridden the negative sign. In this case you need to respect the regional settings, this is the reason of the warning. You can also change the negative sign programatically:

    CultureInfo culture = Thread.CurrentThread.CurrentCulture;
    // Make a writable clone
    culture = (CultureInfo) culture.Clone();
    culture.NumberFormat.NegativeSign = "!";

It's weird; I would have expected 50.ToString(CultureInfo.CreateSpecificCulture("ar-AE")) to return "٥٠", but it doesn't.

I've just looked this up, and the problem seems to be that NumberFormatInfo.DigitSubstitution isn't actually implemented

The DigitSubstitution property is reserved for future use. Currently, it is not used in either parsing or formatting operations for the current NumberFormatInfo object.

So, although there is an enumeration System.Globalization.DigitShapes, it's not actually implemented in the NumberFormatInfo bit of IFormatProvider.