在 .NET core c# 控制台应用程序中调用 Node Http Triggered azure 函数

Question

I have a Node Http triggered azure function that returns an array in the response body. I want to call this function inside a C# console application and access the array returned by the azure function. My azure function returns the expected response body when I hit it on postman. However this is not the case when I call this endpoint on the c# application as I'm getting a response object with status 200 but content-length is -1. Please note if I do the same call for a normal express application in the c# application, I'm able to get the expected response

Here is my azure function

    const httpTrigger: AzureFunction = async function (context: Context, req: HttpRequest): Promise<void> {

    context.log('HTTP trigger function processed a request.');
    const adresses = req.body && req.body.adresses;

    if (adresses) {

        //make an asyn function call
        const locationsPromise = await adresses.map(async (address) => await getLocationCoordinates(address));
        const resolvedLocations = await Promise.all(locationsPromise);
        context.res = await {
            // status: 200, /* Defaults to 200 */
            body:{ data: resolvedLocations}
        };
    }
    else {
        context.res = await  {
            status: 400,
            body: "Please pass a adresses in the request body"
        };
    }
};

Here is my C# code I'm using for the call

  {
    string[] adresses = new string[] { "nairobi", "nakuru", "kericho" };
    string apiUrl = "http://localhost:7071/api/Adress-call";
    Dictionary<string, string[]> postData1 = new Dictionary<string, string[]>()
    {
        { "adresses", adresses },

    };

    var postData = JsonConvert.SerializeObject(postData1);
    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(apiUrl);
    request.Method = "POST";
    request.ContentType = "application/json";
    request.ContentLength = postData.Length;
    using (Stream webStream = request.GetRequestStream())
    using (StreamWriter requestWriter = new StreamWriter(webStream, Encoding.ASCII))
    {
        requestWriter.Write(postData);
    }
    try
    {
        WebResponse response = request.GetResponse();
        using (Stream responseStream = response.GetResponseStream())
        {
            StreamReader reader = new StreamReader(responseStream, Encoding.UTF8);
            DataTable ds = new DataTable();
            var pageViewModel = JsonConvert.DeserializeObject<List<LocationModel>>(reader.ReadToEnd());

        }
    }
    catch (WebException ex)
    {
        WebResponse errorResponse = ex.Response;
        using (Stream responseStream = errorResponse.GetResponseStream())
        {
            StreamReader reader = new StreamReader(responseStream, Encoding.GetEncoding("utf-8"));
            String errorText = reader.ReadToEnd();
            // log errorText
        }
        throw;
    }


}

Answer 1

The Content-Header may be missing from the response. If you check the HttpWebResponse.ContentLength you'll get a -1 . As the docs explain:

If the Content-Length header is not set in the response, ContentLength is set to the value -1.

HttpWebRequest and HttpWebResponse are really old classes that are largely replaced by HttpClient, especially in .NET Core. There were no nullable value types back when these classes were created, so they can only return -1 .

All of this should be replaced with HttpClient. The code isn't just simpler, the class itself is thread-safe and can be reused. It caches sockets underneath, which means the app doesn't have to pay the DNS resolution tax each time it tries to call the same endpoint :

var data=new { adresses = new [] { "nairobi", "nakuru", "kericho" }};
var postData = JsonConvert.SerializeObject(data);
var content=new StringContent(data,Encoding.UTF8,"application/json");

var response=await client.PostAsync(content);

At this point you can inspect the status code :

if (response.StatusCode == ...) // Check status code here.
{
 ...
}

The Content-Length is a Content header. It may be missing, in which case the ContentLength property will be null :

if (response.Content.Headers.ContentLength!=null)
{
    long length=response.Content.Headers.ContentLength.Value;
    //Use the Content length here
}

Or, using pattern matching :

if (response.Content.Headers.ContentLength is long length)
{    
    //Use the Content length here
}

Finally, you can read the response as a string with ReadAsStringAsync and deserialize it. That method will take care of decoding the response body :

var json=await response.Content.ReadAsStringAsync();
var models=JsonConvert.DeserializeObject<List<LocationModel>>(json);