.NET中Google Routes API突然返回空值的问题求助

此前可正常从Google Routes API获取出行路线的代码，如今运行仅返回空对象{}。已确认API账单余额充足，调整多个字段后问题仍未解决，代码一个月前可正常运行，寻求问题原因。

请求代码 #

string routesAPIurl = "https://routes.googleapis.com/directions/v2:computeRoutes";
WebRequest request = WebRequest.Create(routesAPIurl);
request.Method = "POST";
//request.Headers["Content-Type"] = "application/json";
request.ContentType = "application/json";
request.Headers["X-Goog-Api-Key"] = "***************************";
request.Headers["X-Goog-FieldMask"] = "routes.legs.steps.transitDetails";

//create transitObject
TransitObject transitO = new TransitObject();
transitO.travelMode = "TRANSIT";
transitO.departureTime = DateTime.Parse("2024-04-17T09:30:00.000Z");
transitO.computeAlternativeRoutes = true;
Origin trnOrigin = new Origin();
trnOrigin.address = "********";
transitO.origin = trnOrigin;
Destination trnDestination = new Destination();
trnDestination.address = "********";
transitO.destination = trnDestination;
TransitPreferences transitPreferences = new TransitPreferences();
transitPreferences.routingPreference = "TRANSIT_ROUTING_PREFERENCE_UNSPECIFIED";
transitPreferences.allowedTravelModes = new string[] { "LIGHT_RAIL", "BUS" }.ToList();
transitO.transitPreferences = transitPreferences;

var data = Encoding.ASCII.GetBytes(JsonConvert.SerializeObject(transitO));
request.ContentLength = data.Length;

using (var stream = request.GetRequestStream())
{
    stream.Write(data, 0, data.Length);
}

var response = (HttpWebResponse)request.GetResponse();

var responseString = new StreamReader(response.GetResponseStream()).ReadToEnd();

实体类代码 #

public class Destination
{
    public string address { get; set; }
}

public class Origin
{
    public string address { get; set; }
}

public class TransitObject
{
    public Origin origin { get; set; }
    public Destination destination { get; set; }
    public string travelMode { get; set; }
    public System.DateTime departureTime { get; set; }
    public bool computeAlternativeRoutes { get; set; }
    public TransitPreferences transitPreferences { get; set; }
}

public class TransitPreferences
{
    public string routingPreference { get; set; }
    public List<string> allowedTravelModes { get; set; }
}

可能的问题原因 #

• 字段掩码限制过严：当前设置的routes.legs.steps.transitDetails仅请求中转详情，若路线无符合条件的中转步骤或API返回结构中该路径不存在，就会返回空对象。可先将掩码改为routes获取完整响应，验证是否有数据返回。
• 日期序列化格式不符：DateTime对象序列化后的格式可能不符合API要求的RFC3339标准。需检查JSON中departureTime的实际值，必要时添加序列化配置强制输出正确格式：

  JsonConvert.SerializeObject(transitO, new JsonSerializerSettings
  {
      DateTimeZoneHandling = DateTimeZoneHandling.Utc,
      DateFormatString = "yyyy-MM-dd'T'HH:mm:ss'Z'"
  })
  

• API字段或规则变更：Google可能微调了v2版本的请求参数或响应结构，比如allowedTravelModes枚举值、transitPreferences字段要求等，需对照官方文档核对参数正确性。
• 编码问题：使用Encoding.ASCII可能导致含非ASCII字符的地址编码错误，建议替换为Encoding.UTF8生成请求内容。
• 地址解析失败：填写的起点/终点地址无法被API正确解析，导致无路线返回。可尝试替换为经纬度（在实体类中添加location字段）验证是否能获取响应。

内容的提问来源于stack exchange，提问作者Ash