Hi, this is my solution in C# 🐿️

    public static void kaprekarNumbers(int p, int q)
    {
        List<int> numbers = new List<int>();
        for (int i = p; i <= q; i++)
        {
            var digits = i.ToString().ToCharArray().Count();
            var square = Math.Pow(i, 2);
            var square_digits = square.ToString().ToCharArray().Count();
            int left = 0;
            int right = 0;
            if (square_digits > 1)
            {
                int digitsForLeft = square_digits - digits;
                left = Convert.ToInt32(square.ToString().Substring(0, digitsForLeft));
                right = Convert.ToInt32(square.ToString().Substring(digitsForLeft));
            }
            else
            {
                right = (int)square;
            }
            if (left + right == i)
                numbers.Add(i);
        }
        Console.WriteLine(numbers.Count > 0 ? string.Join(" ", numbers) : "INVALID RANGE");
    }