public static class AccessToken
{
  // 有效期30天，緩存獲取的 access token
  public static String TOKEN = null;

  // 百度云中開通對(duì)應(yīng)服務(wù)應(yīng)用的 API Key
  private static String clientId = "API Key";
  // 百度云中開通對(duì)應(yīng)服務(wù)應(yīng)用的 Secret Key
  private static String clientSecret = "Secret Key";

  public static String getAccessToken()
  {
    if (String.IsNullOrEmpty(TOKEN))
    {
      String authHost = "https://aip.baidubce.com/oauth/2.0/token";
      HttpClient client = new HttpClient();
      List<KeyValuePair<String, String>> paraList = new List<KeyValuePair<string, string>>();
      paraList.Add(new KeyValuePair<string, string>("grant_type", "client_credentials"));
      paraList.Add(new KeyValuePair<string, string>("client_id", clientId));
      paraList.Add(new KeyValuePair<string, string>("client_secret", clientSecret));

      HttpResponseMessage response = client.PostAsync(authHost, new FormUrlEncodedContent(paraList)).Result;
      String result = response.Content.ReadAsStringAsync().Result;
      JObject jr = JObject.Parse(result);

      TOKEN = jr.Value<string>("access_token");
    }
    return TOKEN;
  } 
}

public class FaceLivenessHelper
{
  // 在線活體檢測(cè)
  public static string FaceVerify(string imgUrl)
  {
    string token = AccessToken.getAccessToken();
    string host = "https://aip.baidubce.com/rest/2.0/face/v3/faceverify?access_token=" + token;
    Encoding encoding = Encoding.Default;
    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(host);
    request.Method = "post";
    request.KeepAlive = true;
    // String str = "[{\"image\":\"sfasq35sadvsvqwr5q...\",\"image_type\":\"BASE64\",\"face_field\":\"age,beauty,expression\"}]";
    String str = "[{\"image\":\"" + imgUrl + "\",\"image_type\":\"URL\",\"face_field\":\"age,beauty,expression\"}]";
    byte[] buffer = encoding.GetBytes(str);
    request.ContentLength = buffer.Length;
    request.GetRequestStream().Write(buffer, 0, buffer.Length);
    HttpWebResponse response = (HttpWebResponse)request.GetResponse();
    StreamReader reader = new StreamReader(response.GetResponseStream(), Encoding.Default);
    string result = reader.ReadToEnd();
    Console.WriteLine("在線活體檢測(cè):");
    Console.WriteLine(result);
    return result;
  }
}

string imgUrl = "------";
string result = FaceLivenessHelper.FaceVerify(imgUrl);
JObject jresult = JObject.Parse(result);
JObject lvresult = jresult.Value<JObject>("result");
// error_code 為 0 時(shí)表示執(zhí)行成功，其它表示失敗
if (jresult.Value<int>("error_code") == 0)
{
  double face_liveness = lvresult.Value<double>("face_liveness");
  // 活體率達(dá)到要求
  if (face_liveness >= 0.995)
  {
    // 通過檢測(cè)
  }
}