404 when calling a c# web api from another c# web forms application

Question

I have created a simple web api and when I access this from IE the web api returns exactly what I expected. However, now I tried to access the same web api from a web forms application using httpclient. But now I get a 404 error. But the api seems to work, because I do receive results when using a browser. Any ideas what goes wrong? This is the code:

 HttpClientHandler handler = new HttpClientHandler()
 {
     UseDefaultCredentials = true
 };

 HttpClient client = new HttpClient(handler);
 client.BaseAddress = new Uri("http://server/appdir");
 client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

 HttpResponseMessage response = client.GetAsync("/api/environment").Result;

if you debug, the request url is the same than your webapi url? — pollirrata
– pollirrata, Commented Oct 21, 2013 at 21:42
I'll leave this to the WCF experts to answer, but until they work their magic...have tried to run wireshark or something similar to see whats going on under the covers? — JFish222
– JFish222, Commented Oct 21, 2013 at 21:43
Oh and just in case its all on one box (connection to localhost), most packet sniffers don't work. For monitoring local host, I've had luck with RawCap netresec.com/?page=RawCap, and this winsock based sniffer from nirsoft: nirsoft.net/utils/socket_sniffer.html — JFish222
– JFish222, Commented Oct 21, 2013 at 21:46
maybe use client.GetAsync("/appdir/api/environment/").Result; ? — Iłya Bursov
– Iłya Bursov, Commented Oct 21, 2013 at 21:49

Josh Crozier · Accepted Answer · 2013-11-01 23:03:55Z

2

This is the code that worked.

 HttpClientHandler handler = new HttpClientHandler()
 {
     UseDefaultCredentials = true
 };

 HttpClient client = new HttpClient(handler);

 client.BaseAddress = new Uri("http://eetmws10v");

 client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

 HttpResponseMessage response = client.GetAsync("/aim2/api/environment").Result;

edited Nov 1, 2013 at 23:03

Josh Crozier

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answered Oct 22, 2013 at 7:38

Ronald

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Comments

Hafiz Adewuyi · Accepted Answer · 2014-12-21 11:36:22Z

Wow. I was experiencing this same error this weekend and I cannot imagine how flimsy the cause of the problem was.

This is what worked for me:

string _baseAddress = "http://localhost/webapi/";
string controllerURL = "api/School";

client.BaseAddress = new Uri(_baseAddress);
string result = client.GetStringAsync("controllerURL").Result.ToString();

The combinations of _baseAddress and controllerURL that caused the 404 error for me are as follows:

string _baseAddress = "http://localhost/webapi/";
string controllerURL = "/api/School";

or

string _baseAddress = "http://localhost/webapi";
string controllerURL = "api/School";

or

string _baseAddress = "http://localhost/webapi";
string controllerURL = "/api/School";

I sincerely hope something is done soon to remove this needless rigidity that is likely to waste many a developer's useful man hours.

Community · Accepted Answer · 2017-05-23 10:30:18Z

1

I work on this problem 2 days,and what work for me is to add custom user agent, like in this link

code

var client = new HttpClient();
client.DefaultRequestHeaders.Add("User-Agent", "Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.2; WOW64; Trident/6.0)");

edited May 23, 2017 at 10:30

CommunityBot

11 silver badge

answered Nov 29, 2016 at 10:46

yehoni amran

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