using System;

using System.Linq;

using System.Text;

​

public static class StringExtension

{

    public static string StripSpaces(this string s)

    {

        return s.Aggregate(new StringBuilder(), (acc, c) =>

        {

            if (c != ' ' || acc.Length == 0 || acc[acc.Length - 1] != ' ')

                acc.Append(c);

            return acc;

        }).ToString();

    }

​

    public static void Main()

    {

        const string input = "     (five leading spaces)     (five internal spaces)     (five trailing spaces)     ";

        Console.WriteLine(" Input: \"{0}\"", input);

        Console.WriteLine("Output: \"{0}\"", StringExtension.StripSpaces(input));

    }

}