c# - 如何从 Azure Function App 中的请求正文中检索字节数据

Question

在 Python 中，我将图像转换为字节。然后，我像这样将字节传递给 Azure HTTP 触发器函数应用端点 URL (Azure 门户)，就像调用 Azure 认知服务时一样。

image_path = r"C:\Users\User\Desktop\bicycle.jpg"
image_data = open(image_path, "rb").read()
print(len(image_data)) # print length to compare later
url = "https://xxxx.azurewebsites.net/api/HTTPTrigger1........."
headers    = {'Content-Type': 'application/octet-stream'}
response = requests.post(url, headers=headers,
                             data=image_data)

但是，我不知道如何在 Azure 门户上的函数应用程序中检索字节数据。我尝试了以下 (C#)，但没有用。似乎 ReadToEndAsync() 并不是要从请求正文中读取字节数据？还是因为HttpRequest？

public static async Task<IActionResult> Run(HttpRequest req, ILogger log)
{
    string requestBody = await new StreamReader(req.Body).ReadToEndAsync();
    byte[] imageBytes = Encoding.ASCII.GetBytes(requestBody); 
    log.LogInformation(imageBytes.Length.ToString());
    // the length logged is totally not the same with len(image_data) in Python

    //ignore the following lines (not related)
    return name != null
    ? (ActionResult)new OkObjectResult("OK")
    : new BadRequestObjectResult("Please pass a name on the query string or in the request body");
}

对此有什么想法吗？我确实知道使用 base64 字符串的解决方法，但我真的很好奇 Azure 认知服务是如何做到的!

提前致谢。

Answer 1

不要使用 ReadToEndAsync()，而是使用 MemoryStream()。 ReadToEndAsync() 用于读取字符串缓冲区，这会弄乱传入的字节数据。使用 CopyToAsync() 然后将内存流转换为字节数组以保留传入的字节数据。

public static async Task<HttpResponseMessage> Run(HttpRequest req, ILogger log)
{
    //string requestBody = await new StreamReader(req.Body).ReadToEndAsync();
    MemoryStream ms = new MemoryStream(); 
    await req.Body.CopyToAsync(ms);
    byte[] imageBytes = ms.ToArray();
    log.LogInformation(imageBytes.Length.ToString());


    // ignore below (not related)
    string finalString = "Upload succeeded";
    Returner returnerObj = new Returner();
    returnerObj.returnString = finalString;
    var jsonToReturn = JsonConvert.SerializeObject(returnerObj);

    return new HttpResponseMessage(HttpStatusCode.OK) {
        Content = new StringContent(jsonToReturn, Encoding.UTF8, "application/json")
    };
}

public class Returner
{
    public string returnString { get; set; }
}

引用/灵感来自: https://weblog.west-wind.com/posts/2017/sep/14/accepting-raw-request-body-content-in-aspnet-core-api-controllers