调用Google Photos mediaItems:search接口遇400错误，如何按日期范围过滤？

调用Google Photos Library API的mediaItems:search接口获取图片列表时，不带POST请求体可正常返回结果，但添加日期范围过滤的请求体后，收到400 Bad Request错误。

调用代码如下：

string requestUri = "https://photoslibrary.googleapis.com/v1/mediaItems:search";
HttpWebRequest webRequest = (HttpWebRequest)WebRequest.Create(requestUri);
webRequest.Method = "POST";
webRequest.Headers.Add(string.Format("Authorization: Bearer {0}", accessToken));
webRequest.ContentType = "application/json";

string bodyData = "{\"pageSize\":25,\"filters\":{\"dateFilter\":{\"ranges\":[{\"startdate\":{\"year\":2023,\"month\":5,\"day\":4},\"endDate\":{\"year\":2023,\"month\":6,\"day\":4}}]}},\"pageToken\":\"\"}";
ASCIIEncoding encoding = new ASCIIEncoding();
byte[] bytes = encoding.GetBytes(bodyData);
webRequest.ContentLength = bytes.Length;
using (Stream requestStream = webRequest.GetRequestStream())
{
    requestStream.Write(bytes, 0, bytes.Length);
}
WebResponse userinfoResponse = await webRequest.GetResponseAsync();

返回错误信息：

The remote server returned an error: (400) Bad Request.

导致400错误的核心问题有两个：

• JSON字段名大小写不匹配：Google API要求驼峰命名，你将startDate误写为startdate，API无法识别该字段。
• 编码方式错误：JSON内容需使用UTF-8编码，ASCII编码无法处理非ASCII字符，可能导致请求体解析失败。

另外，空的pageToken可以直接省略，无需传入空字符串。

修改后的HttpWebRequest代码 #

string requestUri = "https://photoslibrary.googleapis.com/v1/mediaItems:search";
HttpWebRequest webRequest = (HttpWebRequest)WebRequest.Create(requestUri);
webRequest.Method = "POST";
webRequest.Headers.Add(string.Format("Authorization: Bearer {0}", accessToken));
// 明确指定UTF-8编码
webRequest.ContentType = "application/json; charset=utf-8";

// 修正startdate为startDate，移除空pageToken
string bodyData = "{\"pageSize\":25,\"filters\":{\"dateFilter\":{\"ranges\":[{\"startDate\":{\"year\":2023,\"month\":5,\"day\":4},\"endDate\":{\"year\":2023,\"month\":6,\"day\":4}}]}}}";
UTF8Encoding encoding = new UTF8Encoding();
byte[] bytes = encoding.GetBytes(bodyData);
webRequest.ContentLength = bytes.Length;
using (Stream requestStream = webRequest.GetRequestStream())
{
    requestStream.Write(bytes, 0, bytes.Length);
}
WebResponse userinfoResponse = await webRequest.GetResponseAsync();

推荐使用HttpClient（更简洁的现代API） #

using System.Net.Http;
using System.Text;
using Newtonsoft.Json;

var httpClient = new HttpClient();
// 设置Authorization头
httpClient.DefaultRequestHeaders.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Bearer", accessToken);

// 用匿名对象构建请求体，避免手动拼接JSON的错误
var requestBody = new
{
    pageSize = 25,
    filters = new
    {
        dateFilter = new
        {
            ranges = new[]
            {
                new
                {
                    startDate = new { year = 2023, month = 5, day = 4 },
                    endDate = new { year = 2023, month = 6, day = 4 }
                }
            }
        }
    }
};

// 序列化对象为JSON，自动处理编码和字段名
string jsonBody = JsonConvert.SerializeObject(requestBody);
var requestContent = new StringContent(jsonBody, Encoding.UTF8, "application/json");

HttpResponseMessage response = await httpClient.PostAsync(requestUri, requestContent);
// 自动抛出HTTP错误（如400、401等），便于调试
response.EnsureSuccessStatusCode();
string responseContent = await response.Content.ReadAsStringAsync();

内容的提问来源于stack exchange，提问作者BrianTW