Format fractional separator of C# decimal - formatting

Question

I'm interacting with a 3rd party system that requires me to send it decimal numbers where s decimal comma must precede the fractional part. If the value has no fractional part the decimal comma must still be present.
So for example
decimal d = 123.45M; //needs to become 123,45
decimal d2 = 345M; //needs to become 345,
Is there an elegant way of formatting .net decimals for this purpose?

Answer 1

It seems like your 3rd party system might simply be using a different Culture. You can set the CultureInfo that you want to use and formatting will do what it needs to for that culture including dates, numbers, and currency.
Example:
CultureInfo culture = new CultureInfo("fr-FR");
Console.WriteLine(string.Format(culture, "{0}", 123.45M));
Output:
123,45
Even if you want to keep the current culture but for a given purpose override just one thing you can override them by:
culture.NumberFormat.NumberDecimalSeparator = ",";
Edit: I've found no way of doing the trailing decimal separator using only the built-in numeric formatting but you might be able to find something looking through the custom numeric format strings. Otherwise you may have to resort to simply testing for d2 % 1 == 0 and manually adding the decimal separator.
Example:
public static string FormatWithTrailing(decimal number)
{
// Change the following culture to the actual desired culture
CultureInfo culture = new CultureInfo("fr-FR");
return number % 1 == 0
? number.ToString(culture) + culture.NumberFormat.NumberDecimalSeparator
: number.ToString(culture);
}
Outputs:
123,45
345,