return new HttpStatusCodeResult(HttpStatusCode.BadRequest);//HttpStatusCode statusCode  枚举 // HttpStatusCode.BadRequest = 400,public HttpStatusCodeResult(HttpStatusCode statusCode);//带参的构造函数 HttpStatusCodeResult 构造函数名      public HttpStatusCodeResult(HttpStatusCode statusCode)      : this(statusCode, (string) null){    //调用两个参数的构造函数}//传递400，(string)null;public HttpStatusCodeResult(int statusCode, string statusDescription)    {      this.StatusCode = statusCode;  //400      this.StatusDescription = statusDescription; //null 空对象}    /// 
获取 HTTP 状态代码。
    /// 
     
      HTTP 状态代码。
         public int StatusCode { get; private set; }    /// 
获取 HTTP 状态说明。
    /// 
     
      HTTP 状态说明。
         public string StatusDescription { get; private set; }//返回400界面或者404界面或其他界面