无法对 Here Maps 定位端点进行异步 Post 调用

Question

当通过 Postman 和 C# WebRequest 测试调用时，它可以工作，但我无法使用带有 PostAsync 或 PostJsonAsync 调用的 HttpClient 执行相同的操作。

错误：不支持的媒体类型，尽管需要并应用 application/json。

var httpClient = new HttpClient();
httpClient.DefaultRequestHeaders
                    .Accept
                    .Add(new MediaTypeWithQualityHeaderValue("application/json"));

var content = new StringContent(data, Encoding.UTF8, "application/json");
var response = await httpClient.PostAsync("https://pos.api.here.com/positioning/v1/locate?app_id={id}&app_code={code}", content);
return response;

StatusCode: 415, ReasonPhrase: 'Unsupported Media Type', Version: 1.1, Content: System.Net.Http.HttpConnection+HttpConnectionResponseContent, Headers:{ Date: Fri, 08 Nov 2019 13:38:37 GMT Server: nginx-clojure Content-Type: application/json Content-Length: 114}

网络请求

HttpWebRequest request = HttpWebRequest.Create(url) as HttpWebRequest;
if (!string.IsNullOrEmpty(data))
{
    request.ContentType =  "application/json";
    request.Method =  "POST";

    using (var streamWriter = new StreamWriter(request.GetRequestStream()))
    {
        streamWriter.Write(data);
        streamWriter.Flush();
        streamWriter.Close();
    }
}

using (HttpWebResponse webresponse = request.GetResponse() as HttpWebResponse)
{
    using (StreamReader reader = new StreamReader(webresponse.GetResponseStream()))
    {
        string response = reader.ReadToEnd();
        return response;
    }
}

Answer 1

我看到了两个不同之处：

您正在 HttpClient 代码中设置 Accept header，而您不在 WebRequest 代码中。这定义了 you 接受的数据类型。如果这个 API 调用没有 return JSON，那么它可能只是说 "I have nothing to say to you then"。您可以尝试删除整行。
您的 HttpClient 代码中的 Content-Type 将是 application/json; charset=utf-8，而您在 WebRequest 代码中将其设置为 application/json。我不明白为什么 charset 会使它窒息，但如果更改 #1 不起作用，您可以尝试直接设置 Content-Type 并查看它是否有任何不同：

var content = new StringContent("");
content.Headers.ContentType = new MediaTypeHeaderValue("application/json");

无法对 Here Maps 定位端点进行异步 Post 调用

Unable to make a Async Post call to Here Maps positioning endpoint

c#

asynchronous

.net-core

here-maps-rest