using System;

using System.Linq;

using System.Text.RegularExpressions;

using System.Collections.Generic;

​

public static class Program

{

    public static void Main()

    {

        string[] aLst = new string[]{"B:1", "C:4", "A:2", "B:-1", "A:2", "D:2"};

        List<string> charCnt = new List<string>();

        //charCnt.Add("0:0");

        string concat = "";

        string val = "";

        foreach (var item2 in aLst)

        {

            string[] val2 = item2.Split(':');

            string first2 = val2[0];

            string second2 = val2[1];

            if (charCnt.Any(str => str.Contains(first2)))

            {

                val = aLst.Where(c => charCnt.Any(f => c.StartsWith(first2))).First().ToString();

                string[] val1 = val.Split(':');

                string first1 = val1[0];

                string second1 = val1[1];

                int newVal1 = Convert.ToInt32(second1);

                int newVal2 = Convert.ToInt32(second2);

                int newVal = newVal1 + newVal2;

                string strVal = first1.ToString() + ":" + newVal;

                int index = charCnt.FindIndex(s => s.StartsWith(first2));

                charCnt[index] = strVal;

            }

            else

            {

                charCnt.Add(item2);

            }

        }

​

        //return charCnt.Any(list => list.Any(item => item.ToString().EndsWith("0")).ToString().ToArray();

        foreach (var item in charCnt.OrderBy(q => q).ToList())

        {

            concat += item + ", "; //Concatenate items from the list

        }

​

        Console.WriteLine(concat.Trim().TrimEnd(','));

    }

}