C# HttpClient handle swedish characters åäö in response

Question

When sending a test request in Burp I get correct values for åäö in Swedish but using HttpClient I only get this character:

I have tried setting the Accept-Language header to sv-SE and sv but with the same result. I have also tried getting GetByteArrayAsync and converting this to UTF-8 but no luck there neither.

private HttpClient client = new HttpClient();

public HttpService()
{
    client.DefaultRequestHeaders.Add("Accept-Language", "sv");
    client.DefaultRequestHeaders.Add("Accept-Charset", "utf-8");
}

public string GetRequest(string url)
{
    using (HttpResponseMessage response = client.GetAsync(url).Result)
    {
        //Same result
        //var byteArray = response.Content.ReadAsByteArrayAsync().Result;
        //var result = Encoding.UTF8.GetString(byteArray, 0, byteArray.Length);
        using (HttpContent content = response.Content)
        {
            var result = content.ReadAsStringAsync().Result;
            return result;
        }
    }

}

Update:

Headers from server:

HTTP/1.1 200 OK
Cache-Control: private
Content-Length: 31903
Content-Type: application/json
Expires: Sun, 14 May 2017 22:00:00 GMT
Server: Microsoft-IIS/8.5
Set-Cookie: ASPSESSIONIDCSACQTRA=<REMOVED>; path=/
X-Powered-By: ASP.NET
Date: Mon, 15 May 2017 13:10:18 GMT

Answer 1

Thank you @RemusRusanu. Working code:

public string GetRequest(string url)
{
    using (HttpResponseMessage response = client.GetAsync(url).Result)
    {
        var byteArray = response.Content.ReadAsByteArrayAsync().Result;
        var result = Encoding.GetEncoding("ISO-8859-1").GetString(byteArray, 0, byteArray.Length);
        return result;
    }
}

Answer 2

Ogglas answer will fix it for åäö but might not work for ÅÄÖ. ISO-8859-1 correspondes to either
- Windows-1252 Western European (Windows). Code page 1252
or
- iso-8859-1 Western European (ISO). Code page 28591

To be sure to get the correct encoding, you might want to use Encoding.GetEncoding(int codePage) instead. For more information about different encoding see, https://docs.microsoft.com/en-us/dotnet/api/system.text.encoding?view=netframework-4.8

Here is an example code where the response string is ABCDEFGHIJKLMNOPQRSTUVWXYZÅÄÖabcdefghijklmnopqrstuvwxyzåäö0123456789!"#¤%&/()=?^*_:;>@£${[]}\\~|<,.-¨'´+

using System.Net.Http;
using log4net;
using System.Text;

namespace Stackoverflow
{
    public static class Enc {

        private static readonly ILog log = LogManager.GetLogger(typeof(Enc));

        public static string GetRequest(HttpClient client, string url, int codepage) {
            using (HttpResponseMessage response = client.GetAsync(url).Result) {
                var byteArray = response.Content.ReadAsByteArrayAsync().Result;
                var result = Encoding.GetEncoding(codepage).GetString(byteArray, 0, byteArray.Length);
                return result;
            }
        }

        public static void Example(HttpClient client, string url) {
            string result1 = GetRequest(client, url, 1252);
            string result2 = GetRequest(client, url, 28591);
            log.Debug(result1);
            log.Debug(result2);
        }
    }
}

This gives output:

ABCDEFGHIJKLMNOPQRSTUVWXYZÅÄÖabcdefghijklmnopqrstuvwxyzåäö0123456789!"#¤%&/()=?^*_:;>@£${[]}\~|<,.-¨'´+"
ABCDEFGHIJKLMNOPQRSTUVWXYZÿÿÿabcdefghijklmnopqrstuvwxyzåäö0123456789!"#¤%&/()=?^*_:;>@£${[]}\~|<,.-¨'´+

where ÿ shows up as a black character xC3? in my logs.