public List <Tenant> GetTenantsByCriteria(string lastNameCriteria, string propertyAddress) { List <Tenant> tenants = new List <Tenant>(); List <char> lastNameInitials = new List <char>(); string[] lastNameCriteriaArray = lastNameCriteria.Split(','); foreach (string part in lastNameCriteriaArray) { if (part.Contains("-")) { lastNameInitials.AddRange(GetCharactersFromRange(part)); } else if (!lastNameInitials.Contains(char.Parse(part))) { lastNameInitials.Add((char.Parse(part))); } } return(TenantData.GetTenantList().Where(t => lastNameInitials.Contains(char.Parse(t.LastName.Substring(0, 1)))).ToList <Tenant>()); // return tenants; }