public static void Main()
double doubleValue = 123.456d;
byte[] doubleAsBytes = BitConverter.GetBytes(doubleValue);
string doubleBase64 = Convert.ToBase64String(doubleAsBytes, 0, doubleAsBytes.Length);
Console.WriteLine(doubleValue);
Console.WriteLine(BitConverter.ToString(doubleAsBytes));
Console.WriteLine(doubleBase64);