今天头又晕了

写了如下代码，还跟踪了半个多小时，没找出来问题

if(strCarId.StartsWith("**"))
                                    {
                                         strCarId.Replace("**","U");
                                    }
                                    else if(strCarId.StartsWith("*"))
                                    {
                                         strCarId.Replace("*","T");
                                    }