using System;

public class Program

{

    public static void Main()

    {

        string valor = "C1B6DF66";

        Single s = ConvertHexToSingle(valor);

        Console.WriteLine(s.ToString());

    }

    public static Single ConvertHexToSingle (string hexVal) {

          try {

              int i=0, j=0;

              byte[] bArray = new byte[4];

              for (i = 0; i <= hexVal.Length-1; i += 2) {

                  bArray[j] = Byte.Parse (hexVal[i].ToString() + hexVal[i + 1].ToString(), System.Globalization.NumberStyles.HexNumber);

                  j += 1;

              }

              Array.Reverse (bArray);

              Single s =  BitConverter.ToSingle (bArray, 0);

              return (s);

          } catch (Exception ex) {

              throw new FormatException ("The supplied hex value is either empty or in an incorrect format.  Use the " +

                  "following format: 00000000", ex);

          }

      }

}