Adding Headers and Post data in RESTfull/HTTP Request in C#

Question

I'm having problems with sending POST request in C# and it seems I misunderstood some HTTP basics. So basically I'm implementing RESTfull service client, which work as follows:

Make POST request with username/password and get token
Use this token in header (Authorization:TOKEN) while making other GET/POST/PUT requests

I use WebRequest to make GET requests (with Authorization header) and it's working. But when I use following code to make PUT requests, service is giving "Authentication failed - not logged in" message back:

String url = String.Format("{0}/{1}", AN_SERVER, app);
WebRequest theRequest = WebRequest.Create(url);
theRequest.Method = "POST";

theRequest.ContentType = "text/x-json";
theRequest.ContentLength = json.Length;
Stream requestStream = theRequest.GetRequestStream();

requestStream.Write(Encoding.ASCII.GetBytes(json), 0, json.Length);
requestStream.Close();


theRequest.Headers.Add("Authorization", authToken);

HttpWebResponse response =  (HttpWebResponse)theRequest.GetResponse();

I must be making minor mistake (at least I hope so) while sending POST request. So what am I doing wrong?

Thanks.

have you tried moving the Headers.Add to before the requestStream? One other thing that looks odd is that there isn't a named parameter passed to the request something like requestStream.Write("json=" + json) — Al W
– Al W, Commented Aug 2, 2011 at 22:23
@AI W: Moving headers before requestStream solved the problem. Why the order is important here? Thank you very much. I spend a day trying to "learn" this, bit 30 minutes of Stackoverflow was more helpful. Can you please write it as an answer so that I can accept it. Thanks again. BTW, it's json object being put into request, not named parameter. — Azho KG
– Azho KG, Commented Aug 2, 2011 at 22:40
Does the server accepts PUT requests for non-authorized services? IIRC PUT (and DELETE) is not enabled by default on some versions of IIS, so it may be the case for other servers as well. — carlosfigueira
– carlosfigueira, Commented Aug 3, 2011 at 4:56
Both PUT and POST are working after the changes suggested by @AI W. SO basically this question is closed. THanks — Azho KG
– Azho KG, Commented Aug 3, 2011 at 20:41
FYI - System.Net.HttpRequestHeader enum has standard HTTP header field names, so you don't have to hard-code strings arbitrarily. HttpRequestHeader.Authorization could be used instead of "Authorization". Also WebRequestMethods.Http.Post. — nekno
– nekno, Commented Aug 6, 2011 at 4:39

stevenrcfox · Accepted Answer · 2011-10-10 13:05:23Z

13

Moving Headers before the request steam works (as per AI W's comment), because the request stream is adding the body.

The way webrequest is implemented internally, you need to finish the header before writing body, and once its in stream format, its ready to send.

If you look at the implementation of webrequest in reflector or some such decompiling tool, you'll be able to see the logic.

Hope this helps

answered Oct 10, 2011 at 13:05

stevenrcfox

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2 Comments

Waylon Flinn Over a year ago

Seems like a pretty poor implementation, I'm not surprised that it caused confusion.

stevenrcfox Over a year ago

Its a tad fussy, but its relatively simple to use once you get used to it. People do tend to bump into the limits of webrequest or webclient relatively quickly, and start to use httpwebrequest instead.

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