C# - 如何从 http 请求中获取 HTTP 状态代码

Question

I have the below code, working as expected (given correct URL etc) as a POST request. Seems I have a problem reading the Status Code (I receive a successful 201, and based on that number I need to continue processing). Any idea how to get the status code?

static async Task CreateConsentAsync(Uri HTTPaddress, ConsentHeaders cconsentHeaders, ConsentBody cconsent)
{
    HttpClient client = new HttpClient();

    try
    {
        client.BaseAddress = HTTPaddress;
        client.DefaultRequestHeaders.Accept.Clear();
        client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("*/*"));
        client.DefaultRequestHeaders.Add("Connection", "keep-alive");
        client.DefaultRequestHeaders.Add("Cache-Control", "no-cache");

        client.DefaultRequestHeaders.Add("otherHeader", myValue);
        //etc. more headers added, as needed...

        HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Post, client.BaseAddress);

        request.Content = new StringContent(JsonConvert.SerializeObject(cconsent, Formatting.Indented), System.Text.Encoding.UTF8, "application/json");

        Console.WriteLine("\r\n" + "POST Request:\r\n" + client.DefaultRequestHeaders + "\r\nBody:\r\n" + JsonConvert.SerializeObject(cconsent, Formatting.Indented) + "\r\n");

        await client.SendAsync(request).ContinueWith
        (
            responseTask => 
            {
                Console.WriteLine("Response: {0}", responseTask.Result + "\r\nBody:\r\n" + responseTask.Result.Content.ReadAsStringAsync().Result);
            }
        );

        Console.ReadLine();
    }
    catch (Exception e)
    {
        Console.WriteLine("Error in " + e.TargetSite + "\r\n" + e.Message);
        Console.ReadLine();
    }
}

Answer 1

There is a Status code in your Result.

responseTask.Result.StatusCode

Or even better

    var response = await client.SendAsync(request);
    var statusCode = response.StatusCode;

Answer 2

• It helps to avoid using ContinueWith if you're already inside an async function because you can use the (much cleaner) await keyword.

• If you await the SendAsync call you'll get a HttpResponseMessage object you can get the status code from:

• Also, wrap your IDisposable objects in using() blocks (except HttpClient - which should be a static singleton or better yet, use IHttpClientFactory ).

• Don't use HttpClient.DefaultRequestHeaders for request-specific headers, use HttpRequestMessage.Headers instead.

• The Connection: Keep-alive header will be sent by HttpClientHandler automatically for you.
• Are you sure you need to send Cache-control: no-cache in the request? If you're using HTTPS then it's almost guaranteed that there won't be any proxy-caches causing any issues - and HttpClient does not use the Windows Internet Cache either.
• Don't use Encoding.UTF8 because it adds a leading byte-order-mark. Use a private UTF8Encoding instance instead.
• Always use .ConfigureAwait(false) with every await on code that does not run in a thread-sensitive context (such as WinForms and WPF).

private static readonly HttpClient _httpClient = new HttpClient();
private static readonly UTF8Encoding _utf8 = new UTF8Encoding( encoderShouldEmitUTF8Identifier: false, throwOnInvalidBytes: true );

static async Task CreateConsentAsync( Uri uri, ConsentHeaders cconsentHeaders, ConsentBody cconsent )
{
    using( HttpRequestMessage req = new HttpRequestMessage( HttpMethod.Post, uri ) )
    {
        req.Headers.Accept.Add( new MediaTypeWithQualityHeaderValue("*/*") );
        req.Headers.Add("Cache-Control", "no-cache");
        req.Headers.Add("otherHeader", myValue);
        //etc. more headers added, as needed...

        String jsonObject = JsonConvert.SerializeObject( cconsent, Formatting.Indented );
        request.Content = new StringContent( jsonObject, _utf8, "application/json");

        using( HttpResponseMessage response = await _httpClient.SendAsync( request ).ConfigureAwait(false) )
        {
            Int32 responseHttpStatusCode = (Int32)response.StatusCode;
            Console.WriteLine( "Got response: HTTP status: {0} ({1})", response.StatusCode, responseHttpStatusCode );
        }
    }
}

Answer 3

You could simply check the StatusCode property of the response:

https://docs.microsoft.com/en-us/previous-versions/visualstudio/hh159080(v=vs.118)?redirectedfrom=MSDN

static async void dotest(string url)
{
    using (HttpClient client = new HttpClient())
    {
        HttpResponseMessage response = await client.GetAsync(url);

        if (response.IsSuccessStatusCode)
        {
            Console.WriteLine(response.StatusCode.ToString());
        }
        else
        {
            // problems handling here
            Console.WriteLine(
                "Error occurred, the status code is: {0}", 
                response.StatusCode
            );
        }
    }
}

Answer 4

@AthanasiosKataras is correct for returning the status code itself but if you would also like to return the status code value (ie 200, 404). You can do the following:

var response = await client.SendAsync(request);
int statusCode = (int)response.StatusCode

The above will give you the int 200.

EDIT:

Is there no reason why you cannot do the following?

using (HttpResponseMessage response = await client.SendAsync(request))
{
    // code
    int code = (int)response.StatusCode;
}