EPPlus/Utils/AddressUtility.cs

using System.Text.RegularExpressions;

namespace OfficeOpenXml.Utils;

public static class AddressUtility {
  public static string ParseEntireColumnSelections(string address) {
    string parsedAddress = address;
    var matches = Regex.Matches(address, "[A-Z]+:[A-Z]+");
    foreach (Match match in matches) {
      AddRowNumbersToEntireColumnRange(ref parsedAddress, match.Value);
    }
    return parsedAddress;
  }

  private static void AddRowNumbersToEntireColumnRange(ref string address, string range) {
    var parsedRange = string.Format("{0}{1}", range, ExcelPackage.MaxRows);
    var splitArr = parsedRange.Split(new[] { ':' });
    address = address.Replace(range, string.Format("{0}1:{1}", splitArr[0], splitArr[1]));
  }
}