using System;

using System.Linq;

public class Program

{

    public static void Main()

    {

        string input = "zf3kabxcde224lkzf3mabxc51+crsdtzf3nab=";

        int patternLength = 3;

​

        var patternCollection = (from i in

                       Enumerable.Range(0, input.Length - patternLength + 1)

                            let pattern = input.Substring(i, patternLength)

                            select pattern)

                                .GroupBy(itm => itm);

        foreach (var pattern in patternCollection)

        {

            if (pattern.Count() > 1)

                Console.WriteLine("Pattern:{0},Count:{1}", pattern.Key, pattern.Count());

        }

    }

}