Extend decimal type to return a formatted currency string

Extend decimal type to return a formatted currency string

public static string ToCurrencyString(this decimal amount, string currency)
{
    var map = new Dictionary<string, string>
    {
	{"USD", "en-us"},
	{"GBP", "en-gb"},
	{"EUR", "de-de"},
	{"AUD", "en-AU"},
	{"CAD", "en-us"}
    };

    if (!map.ContainsKey(currency))
	throw new Exception("Unsupported currency: " + currency);

    return string.Format(CultureInfo.CreateSpecificCulture(map[currency]), "{0:C}", amount);
}