本地运行ASP.NET Core调用Azure Computer Vision时遇HTTP请求未知错误

我创建了一个ASP.NET Core Web API项目，用于和Azure Computer Vision实例通信生成图像标题。使用密钥凭据完成认证（后续计划切换为托管标识），代码部署到Azure App Service后运行完全正常，但本地运行时出现错误，而用curl直接从本地请求Azure Computer Vision实例却没有问题。

调用代码（C#） #

var serviceOptions = new VisionServiceOptions(
    "https://NAME.cognitiveservices.azure.com/",
    new AzureKeyCredentials("KEY"));

using var imageSource = VisionSource.FromUrl(
     new Uri("https://learn.microsoft.com/azure/cognitive-services/computer-vision/media/quickstarts/presentation.png"));

var analysisOptions = new ImageAnalysisOptions()
{
    Features =
          ImageAnalysisFeature.CropSuggestions
        | ImageAnalysisFeature.Caption
        | ImageAnalysisFeature.DenseCaptions
        | ImageAnalysisFeature.Objects
        | ImageAnalysisFeature.People
        | ImageAnalysisFeature.Text
        | ImageAnalysisFeature.Tags
};

var analyzer = new ImageAnalyzer(serviceOptions, imageSource, analysisOptions);

var result = analyzer.Analyze();

if (result.Reason == ImageAnalysisResultReason.Analyzed)
{
    return Ok(result);
}

return NotFound(ImageAnalysisErrorDetails.FromResult(result));

本地运行错误信息 #

{
  "message": "Unknown error in sending http request",
  "errorCode": -1,
  "reason": 5
}

正常工作的curl命令 #

curl -H "Ocp-Apim-Subscription-Key: KEY" -H "Content-Type: application/json" "https://NAME.cognitiveservices.azure.com/computervision/imageanalysis:analyze?features=caption,read&model-version=latest&language=en&api-version=2023-02-01-preview" -d "{'url':'https://learn.microsoft.com/azure/ai-services/computer-vision/media/quickstarts/presentation.png'}"

排查与解决建议 #

• 检查本地代理配置：如果本地走代理，SDK可能未自动获取代理设置。可以手动为HttpClient指定代理：

  var handler = new HttpClientHandler
  {
      UseProxy = true,
      Proxy = new WebProxy("http://你的代理地址:端口")
  };
  var httpClient = new HttpClient(handler);
  var analyzer = new ImageAnalyzer(serviceOptions, imageSource, analysisOptions, httpClient);
  

• 更新SDK版本：确认Azure.AI.Vision.ImageAnalysis SDK为最新稳定版，旧版本可能存在本地网络适配问题，通过NuGet更新即可。
• 排查防火墙/安全软件：本地防火墙或杀毒软件可能拦截了SDK的HTTPS请求，可暂时关闭测试，若恢复正常则添加放行规则。
• 指定TLS版本：尝试强制使用TLS 1.2发起请求，避免版本兼容问题：

  System.Net.ServicePointManager.SecurityProtocol = System.Net.SecurityProtocolType.Tls12;
  

• 核对本地配置：检查本地开发环境配置文件（如appsettings.Development.json）中的端点URL和密钥是否与curl中的完全一致，排除配置错误。

内容的提问来源于stack exchange，提问作者J Heschl