Double String Format Extensions

For the Microsoft documentation see see here
Makes writing numeric types as a formatted number much easier. Here it is set for double types:

void Main()
{
	Console.WriteLine(1234.567.ToFixedDpFormat(2));      // =>  1234.57
	Console.WriteLine(1234.567.ToNumSigDigitsFormat(3)); // =>  1.23E+03
	Console.WriteLine(1234.567.ToCulturalFormat(2));     // =>  1,234.57
	Console.WriteLine(1234.567.ToCurrencyFormat());      // => £1,234.57

	Console.WriteLine(1234d.ToFixedDpFormat(2));            // =>  1234.00
	Console.WriteLine(1.2340.ToNumSigDigitsFormat(3));      // =>     1.23
	Console.WriteLine(123445677.345234.ToCulturalFormat(2));// => 123,445,677.35
	Console.WriteLine(1234345.567.ToCurrencyFormat());      // => £1,234,345.57
}

namespace Common.Extensions.DoubleToStringFormatting
{
  public static class DoubleToStringExtensions
  {
    public static string ToFixedDpFormat(this double number, int numDP = 0)
    {
      var res = number.ToString($"F{numDP}"); // ToFixedDpFormat(1234.567,2) (en - US) -> 1234.57
      return res;
    }


    public static string ToNumSigDigitsFormat(this double number, int numSigDig = 3)
    {
      var res = number.ToString($"G{numSigDig}"); // ToNumSigDigitsFormat(123.4546) en-US -> 124.0
      return res;
    }

    // Prettifies the string according to cultural aesthetics and the specified num of DP
    public static string ToCulturalFormat(this double number, int numDP = 2)
    {
      var res = number.ToString($"N{numDP}");
      return res;
    }

    // Converts to a currency (using the default cultural currency sign)
    public static string ToCurrencyFormat(this double number, int numDP = 2)
    {
      var res = number.ToString($"C{numDP}"); // ToCurrencyFormat(123.456), en-US -> $123.46
      return res;
    }
  }
}

Something similar can be used for float,decimal and int types as well.