Convert.ToString Method (Double, IFormatProvider)

// Define an array of numbers to display. 
double[] numbers = { -1.5345e16, -123.4321, 19092.123, 1.1734231911290e16 };
// Define the culture names used to display them. 
string[] cultureNames = { "en-US", "fr-FR", "ja-JP", "ru-RU" };

foreach (double number in numbers)
{
   Console.WriteLine("{0}:", Convert.ToString(number,
                             System.Globalization.CultureInfo.InvariantCulture));
   foreach (string cultureName in cultureNames)
   {
      System.Globalization.CultureInfo culture = new System.Globalization.CultureInfo(cultureName);
      Console.WriteLine("   {0}: {1,20}",
                        culture.Name, Convert.ToString(number, culture));
   }
   Console.WriteLine();
}   
// The example displays the following output: 
//    -1.5345E+16: 
//       en-US:          -1.5345E+16 
//       fr-FR:          -1,5345E+16 
//       ja-JP:          -1.5345E+16 
//       ru-RU:          -1,5345E+16 
//     
//    -123.4321: 
//       en-US:            -123.4321 
//       fr-FR:            -123,4321 
//       ja-JP:            -123.4321 
//       ru-RU:            -123,4321 
//     
//    19092.123: 
//       en-US:            19092.123 
//       fr-FR:            19092,123 
//       ja-JP:            19092.123 
//       ru-RU:            19092,123 
//     
//    1.173423191129E+16: 
//       en-US:   1.173423191129E+16 
//       fr-FR:   1,173423191129E+16 
//       ja-JP:   1.173423191129E+16 
//       ru-RU:   1,173423191129E+16