var ltCode = from item in psw.VehicleInsuranceItem select item.Code;
string code = string.Join("|", ltCode.ToArray());

string 转List<string>
List<string> ltCodes = new List<string>(System.Text.RegularExpressions.Regex.Split(code, "|"));

List<string> ltCodes = new List<string>(code.Split(new string[] { ", " }, StringSplitOptions.RemoveEmptyEntries));