爬虫发起抓取被服务器拒绝访问返回403禁止访问解决方案

try
            {
               //这里调用api接口
            }
            catch (WebException ex)
            {
                var strm = ex.Response.GetResponseStream();
                strm.Position = 0;
                StreamReader reader = new StreamReader(strm);
                string error = reader.ReadToEnd();
                //这里看error里面的值是否有你想要的值
                if (!string.IsNullOrWhiteSpace(error))
                {
                    var result = JsonConvert.DeserializeObject<JObject>(error)["result"]["results"];
                    if (result == null)
                        return null;
                    var customer = JsonConvert.DeserializeObject<JArray>(result.ToString());
                    if (customer == null)
                        return null;
                    List<InvTitle> list = new List<InvTitle>();
                    foreach (var item in customer)
                    {
                        InvTitle mc = new InvTitle()
                        {
                            Name = item["entName"] != null ? item["entName"].ToString() : "",
                            TaxCode = item["credCode"] != null ? item["credCode"].ToString() : "",
                            State = "y",
                            CreateTime = DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss"),
                            UpdateTime = DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss")
                        };
                        list.Add(mc);
                        if (list.Count == 4)
                            break;
                    }
                    return list;
                }

                return null;
            }