using System;

using System.Linq;

​

    public static class ExtensionMethods

    {

        public static bool FuzzyCompare(this string lhs, string rhs, float ratioRequired)

        {

            var matchingLetters =  lhs.Zip

                ( 

                    rhs, 

                    (a,b) => a == b ? 1 : 0

                )

                .Sum();

            Console.WriteLine("{0} letters match", matchingLetters);

            return (float)matchingLetters / (float)lhs.Length > ratioRequired;

        }

    }

    public class Program

    {

        public static void Main()

        {

            var a = "ABCDE";

            var b = "ABCDEFGHI";

            Console.WriteLine( a.FuzzyCompare(b, 0.5F) );

        }

    }