hiimray-co-uk-www-posts/2021/02/SpreadsheetCoord.cs

using System;

namespace WindowsFormsApp1
{
    public class SpreadsheetCoord
    {
        public static string ConvertToColumnCode(int columnNo, int rowNo)
        {
            if ((columnNo <= 0) || (rowNo <= 0)) return null;

            string rs = string.Empty;

            int x = 790;
            while (x > 0)
            {
                int n = (x % 26);

                rs = Convert.ToChar(65 + n - 1) + rs;

                x -= n;
                x = (x / 26);
            }

            return string.Concat(rs, rowNo.ToString());
        }

        public static Tuple<int, int> ConvertToCoord(string value)
        {
            bool checkAlpha = true;
            string alpha = string.Empty;
            string digit = string.Empty;

            for (int i = 0; i < value.Length; i++)
            {
                if (checkAlpha)
                {
                    if (isAlpha(value[i]))
                    {
                        alpha += value[i];
                    }
                    else if (isDigit(value[i]))
                    {
                        digit += value[i];

                        checkAlpha = false;
                    }
                    else
                    {
                        return null;
                    }
                }
                else
                {
                    if (isAlpha(value[i]))
                    {
                        return null;
                    }
                    else if (isDigit(value[i]))
                    {
                        digit += value[i];
                    }
                    else
                    {
                        return null;
                    }
                }
            }

            // no alpha or digits
            if ((alpha.Length <= 0) || (digit.Length <= 0))
            {
                return null;
            }

            int rowNo;
            if (!int.TryParse(digit, out rowNo))
            {
                return null;
            }

            if (rowNo <= 0)
            {
                return null;
            }

            int columnNo = convertColumn(alpha);

            return new Tuple<int, int>(columnNo, rowNo);
        }

        public static bool IsValid(string value)
        {
            bool checkAlpha = true;
            string alpha = string.Empty;
            string digit = string.Empty;

            for (int i = 0; i < value.Length; i++)
            {
                if (checkAlpha)
                {
                    if (isAlpha(value[i]))
                    {
                        alpha += value[i];
                    }
                    else if (isDigit(value[i]))
                    {
                        digit += value[i];

                        checkAlpha = false;
                    }
                    else
                    {
                        return false;
                    }
                }
                else
                {
                    if (isAlpha(value[i]))
                    {
                        return false;
                    }
                    else if (isDigit(value[i]))
                    {
                        digit += value[i];
                    }
                    else
                    {
                        return false;
                    }
                }
            }

            // no alpha or digits
            if ((alpha.Length <= 0) || (digit.Length <= 0))
            {
                return false;
            }

            int n;
            if (!int.TryParse(digit, out n))
            {
                return false;
            }

            if (n <= 0)
            {
                return false;
            }

            return true;
        }

        protected static int convertColumn(string value)
        {
            int rv = 0;

            int len = value.Length - 1;
            for (int i = len; i >= 0; i--)
            {
                int n = (len - i);
                int x = convertColumn(value[i]);

                rv += (int)(x * Math.Pow(26, n));
            }

            return rv;
        }

        protected static int convertColumn(char value)
        {
            if (isAlpha(value))
            {
                int code = Convert.ToInt16(char.ToUpper(value));

                return (code - 65) + 1;
            }
            else
            {
                return 0;
            }
        }


        protected static bool isAlpha(char value)
        {
            int code = Convert.ToInt16(char.ToUpper(value));

            return ((code >= 65) && (code <= 90));
        }

        protected static bool isDigit(char value)
        {
            int code = Convert.ToInt16(char.ToUpper(value));

            return ((code >= 48) && (code <= 57));
        }

    }
}