文字列を2進数または10進数にして、特定のロケールに適した形式に変換したら、
double amount = 1234.95;
amount.ToString("C")
amount.ToString("C", System.Globalization.CultureInfo.GetCultureInfo("en-ie"))
amount.ToString("C", System.Globalization.CultureInfo.GetCultureInfo("es-es"))
amount.ToString("C", System.Globalization.CultureInfo.GetCultureInfo("en-GB"))
amount.ToString("C", System.Globalization.CultureInfo.GetCultureInfo("en-au"))
amount.ToString("C", System.Globalization.CultureInfo.GetCultureInfo("en-us"))
amount.ToString("C", System.Globalization.CultureInfo.GetCultureInfo("en-ca"))
PadLeft(12,'0')て文字列を使用する場合