using System;

public class Program

{

    public abstract class StringHandler

    {

        protected StringHandler _next;

        public void SetNext(StringHandler next)

        {

          _next = next;

        }

        public abstract string Execute(string s);

    }

    public class StringUpperCaseHandler : StringHandler {

        public override string Execute(string s)

        {

            s = s.ToUpper();

            if (_next != null)

            {

                s = _next.Execute(s);

            }

            return s;

        }

    }

    public class StringTrimStartHandler : StringHandler {

        public override string Execute(string s)

        {

            s = s.TrimStart(',');

            if (_next != null)

            {

                s = _next.Execute(s);

            }

            return s;

        }

    }

    public class StringTrimEndHandler : StringHandler {

        public override string Execute(string s)

        {

            s = s.TrimEnd(',');

            if (_next != null)

            {

                s = _next.Execute(s);

            }

            return s;

        }

    }

    public static void Main()

    {

        StringHandler h1 = new StringUpperCaseHandler();

        StringHandler h2 = new StringTrimEndHandler();

        StringHandler h3 = new StringTrimStartHandler();

​

        h1.SetNext(h2);

        h2.SetNext(h3);

        Console.WriteLine(h1.Execute(",, hello,,"));

    }

}