public class HttpHelper
  {
    private readonly IHttpClientFactory _httpClient;
    public HttpHelper(IHttpClientFactory httpClient)
    {
      _httpClient = httpClient;
    }

    public async Task<string> HttpGet(string url, string param)
    {
      var client = _httpClient.CreateClient();
      var response = await client.GetStringAsync( url );
      TokenResultModel model = JsonConvert.DeserializeObject<TokenResultModel>( response );
      return model.desc;
    }

    public async Task<object> HttpPost(string url,string param, Dictionary<string, string> head)
    {
      var client = _httpClient.CreateClient();
      var content = new StringContent( param, Encoding.UTF8 );
      foreach (var item in head)
      {
　　　　 //表头字段中含有特殊字符"/"
        client.DefaultRequestHeaders.TryAddWithoutValidation( item.Key, item.Value );
      }
      HttpResponseMessage response =client.PostAsync( url, content ).Result;
      var data = response.Content.ReadAsStringAsync().Result;
      return data;
    }
  }