列=名字、姓氏、聘用日期、中间名等，
传入值= Col1$Col2_Col3
这些col 1，col 2，col 3是列名称，它们之间将添加特殊字符。现在需要拆分此字符串，并使用linq将根据列从数据库中替换值。在接收到值后，需要以相同的格式将其连接起来，并在中间添加特殊字符，然后返回字符串。
这里我已经附上了一段代码，我试图实现上述问题。
预期返回值“Rob$Steve_Liam”

public string AutoCredential(string credential, int employeeID)
        {
            Char[] specialChar = { '_', '$', '&' };

            string? format = _itzmeinContext.AppSettings.Where(a => a.AppKey == credential).Select(a => a.AppValue).FirstOrDefault();

            var userTypes = _itzmeinContext.GlobalLookupData.Where(ut => ut.GlobalLookupTableNameId == 7).
                            Select(ut => ut.LookupName).ToList();

            var unFormat = format.Split(specialChar);

            var s = unFormat.Intersect(userTypes);

            string FirstName = null!;
            string MiddleName = null!;
            string LastName = null!;
            string EmailId = null!;
            string PrimaryContactNumber = null!;
            string SecondaryContactNumber = null!;
            string HireDate = null!;

            if (s.Contains("FirstName"))
            {
                FirstName = _smasContext.Users.Where(u => u.UserId == employeeID).Select(u => u.FirstName).FirstOrDefault();
            }
            
            if (s.Contains("MiddleName"))
            {
                MiddleName = _smasContext.Users.Where(u => u.UserId == employeeID).Select(u => u.MiddleName).FirstOrDefault();
            }

            if (s.Contains("LastName"))
            {
                LastName = _smasContext.Users.Where(u => u.UserId == employeeID).Select(u => u.LastName).FirstOrDefault();
            }

            if (s.Contains("EmailId"))
            {
                EmailId = _smasContext.Users.Where(u => u.UserId == employeeID).Select(u => u.EmailId).FirstOrDefault();
            }

            if (s.Contains("PrimaryContactNumber"))
            {
                PrimaryContactNumber = _smasContext.Users.Where(u => u.UserId == employeeID).Select(u => u.PrimaryContactNumber).FirstOrDefault();
            }

            if (s.Contains("SecondaryContactNumber"))
            {
                SecondaryContactNumber = _smasContext.Users.Where(u => u.UserId == employeeID).Select(u => u.SecondaryContactNumber).FirstOrDefault();
            }

            if (s.Contains("HireDate"))
            {
                HireDate = _smasContext.Users.Where(u => u.UserId == employeeID).Select(u => u.HireDate.Date.Year.ToString()).FirstOrDefault();
            }

            string result = string.Concat(FirstName + MiddleName + LastName + EmailId + PrimaryContactNumber + SecondaryContactNumber + HireDate);
            
            return result;
           
        }