solution.cs

class Solution
{
    static void Main(string[] args)
    {
        int L = int.Parse(Console.ReadLine());
        int H = int.Parse(Console.ReadLine());
         
        var writter = new Writer(H,L);
         
        string T = Console.ReadLine();
        for (int i = 0; i < H; i++)
        {
            writter.PopulateLetters(Console.ReadLine());
        }
        writter.ToAsciiString(T, true);
         
    }
}
class Letter
{
        public int height { get; private set; }
        public int width { get; private set; }
        public int startPoint { get; private set; }
        public List<string> AsciiMatrix;
        private Letter() { }
        public Letter(int h, int w, int s)
        {
            AsciiMatrix = new List<string>();
            height = h;
            width = w;
            startPoint = s;
        }
        public void AddRow(string row)
        {
            AsciiMatrix.Add(row.Substring(this.startPoint, width));
        }
    }
class Writer
{
        public Dictionary<char, Letter> dict = new Dictionary<char, Letter>();
        private string charList = "ABCDEFGHIJKLMNOPQRSTUVWXYZ?";
        private int height;
        public Writer(int h, int w)
        {
            charList
                .ToCharArray()
                .ToList()
                .ForEach(c => dict.Add(c, new Letter(h, w, charList.IndexOf(c) * w )));
            height = h;
        }
        public void PopulateLetters(string row)
        {
            foreach (KeyValuePair<char, Letter> entry in dict)
            {
                entry.Value.AddRow(row);
            }
        }
        public List<string> ToAsciiString(string s, bool print)
        {
            var searchString = string.Join("" , s.ToUpper().ToCharArray().ToList().Select(x =>
            {
                return charList.Contains(x) ? x : '?';
            }).ToList());
             
            List<string> buffer = new List<string>();
            for (int i = 0; i < height; i++)
            {
                List<string> lineBuffer = new List<string>();
                searchString.ToCharArray().ToList().ForEach(e =>
                {
                    lineBuffer.Add(dict[e].AsciiMatrix[i]);
                });
                 
                buffer.Add(string.Join("", lineBuffer));
            }
            foreach(string row in buffer){
                Console.WriteLine($"{row}");
            }
            return buffer;
        }
    }