using System;

using System.Text;

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine(SplitToMaxLength("Hello World", 10));

        Console.WriteLine(SplitToMaxLength("abcdefghijklmnopqrstuvwxyz", 20));

        Console.WriteLine(SplitToMaxLength("abcdefghijklmnopqrstuvwxyz", 8));

    }

​

    public static string SplitToMaxLength(string s, int maxLength)

    {

        if (string.IsNullOrEmpty(s) == false && maxLength > 1 && s.Length > maxLength)

        {

            var sb = new StringBuilder();

            //E.g. abcdefghijklmnopqrstuvwxyz

            //E.g. maxLength: 20

            //E.g. 9

            var splitLength = (int)(Math.Floor(maxLength / (double)2) - 1);

            //Take the left part of the string

            //E.g. abcdefghi

            sb.Append(s.Substring(0, splitLength));

            //Merge together with two dots                 

            sb.Append("..");

            //Take the right part of the string

            //E.g. rstuvwxyz

            sb.Append(s.Substring(s.Length - splitLength, splitLength));

            //E.g, result: abcdefghi..rstuvwxyz

            return sb.ToString();

        }

​

        return s;

    }

}