Rayvor

using System.Text.RegularExpressions;

public static class RegexEx
{
        public static string ReplaceEx(this string input, string pattern, string replacement)
        {
            return Regex.Replace(input, pattern, replacement);
        }
}

string line = "123";
string result = line.ReplaceEx("1", "111").ReplaceEx("2", "222").ReplaceEx("3", "333");
Console.WriteLine(result); // 111222333

Mapper.Initialize(cfg => cfg.CreateMap<UsersEntity, UsersContainer>));

var users = _mapper.Map<IEnumerable<UsersContainer>, List<UsersEntity>>(entities);