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Web API Read Response on 400

The Stackoverflow API, if the request is not successful, how to read the response please?
using (HttpClient Client = new HttpClient(handler))
{
string response = string.Empty;
response = Client.GetStringAsync(apiUri.Uri).Result;
return JsonConvert.DeserializeObject<Questions<Question>>(response);
}
When an error occurs:
{"error_id":502,"error_message":"too many requests from this IP, more requests available in 82216 seconds","error_name":"throttle_violation"}
An error InnerException = {"Response status code does not indicate success: 400 (Bad Request)."}

The following paragraph is from Call a Web API From a .NET Client (C#)
HttpClient does not throw an exception when the HTTP response contains an error code. Instead, the IsSuccessStatusCode property is false if the status is an error code. If you prefer to treat HTTP error codes as exceptions, call HttpResponseMessage.EnsureSuccessStatusCode on the response object. EnsureSuccessStatusCode throws an exception if the status code falls outside the range 200–299. Note that HttpClient can throw exceptions for other reasons — for example, if the request times out.
In your case the code could be something like the following.
var response = await client.GetAsync(apiUri.Uri);
if (!response.IsSuccessStatusCode)
{
var text = await response.Content.ReadAsStringAsync();
// Log error
return null; // throw etc.
}
else
{
var text = await response.Content.ReadAsStringAsync();
var o = JsonConvert.DeserializeObject<Questions<Question>>(o);
return o;
}
(You can move var text = ... outside of if if you wish.)
Status code can be examined instead of calling IsSuccessStatusCode, if needed.
if (response.StatusCode != HttpStatusCode.OK) // 200
{
throw new Exception(); / return null et.c
}

c# HttpWebRequest and HttpWebResponse generic stuff

I am playing around with an app using HttpWebRequest to dialog with a web server.
I followed standard instructions I found on the web to build my request function that I tried to make as generic as possible (I try to get a unique method regardless of the method: PUT, POST, DELETE, REPORT, ...)
When I submit a "REPORT" request, I get two access logs on my server:
1) I get response 401 after following line is launched in debugger
reqStream.Write(Encoding.UTF8.GetBytes(body), 0, body.Length);
2) I get response 207 (multi-get, which is what I expect) after passing the line calling Request.GetResponse();
Actually, it seems to be the Request.GetRequestStream() line that is querying the server the first time, but the request is only committed once passing the reqStream.Write(...) line...
Same for PUT and DELETE, the Request.GetRequestStream() again generates a 401 access log on my server whereas the Request.GetResponse(); returns code 204.
I don't understand why for a unique request I have two server access logs, especially one that seems to be doing nothing as it always returns code 401... Could anybody explain what is going on? Is it a flaw in my code or a bad design due to my attempt to get a generic code for multiple methods?
Here is my full code:
public static HttpWebResponse getHttpWebRequest(string url, string usrname, string pwd, string method, string contentType,
string[] headers, string body) {
// Variables.
HttpWebRequest Request;
HttpWebResponse Response;
//
string strSrcURI = url.Trim();
string strBody = body.Trim();
try {
// Create the HttpWebRequest object.
Request = (HttpWebRequest)HttpWebRequest.Create(strSrcURI);
// Add the network credentials to the request.
Request.Credentials = new NetworkCredential(usrname.Trim(), pwd);
// Specify the method.
Request.Method = method.Trim();
// request headers
foreach (string s in headers) {
Request.Headers.Add(s);
}
// Set the content type header.
Request.ContentType = contentType.Trim();
// set the body of the request...
Request.ContentLength = body.Length;
using (Stream reqStream = Request.GetRequestStream()) {
// Write the string to the destination as a text file.
reqStream.Write(Encoding.UTF8.GetBytes(body), 0, body.Length);
reqStream.Close();
}
// Send the method request and get the response from the server.
Response = (HttpWebResponse)Request.GetResponse();
// return the response to be handled by calling method...
return Response;
}
catch (Exception e) {
throw new Exception("Web API error: " + e.Message, e);
}

GetResponse() in API call causes (400) Bad Request error

I am very new to programming.
I'm setting up a loop that continuously send a POST request to a site through the REST API. The POST request works properly and the way I intend.
I would like to add functionality that requires the response from this post. However, every way of retrieving the response gives me an error:
"An unhandled exception of type 'System.Net.WebException' occurred in System.dll
Additional information: The remote server returned an error: (400) Bad Request."
As I debug line by line, it seems that the "GetResponse()" line causes this each time, and causes the program to break. If I remove this line, the program works properly and throws no errors.
Hoping someone can assist. Here is what I have written:
string URL= "https:.......";
HttpWebRequest apiCall = (HttpWebRequest)WebRequest.Create(airWatchURL);
apiCall.Method = "POST";
apiCall.Headers.Add(HttpRequestHeader.Authorization, auth);
apiCall.Headers.Add("aw-tenant-code", apiKey);
apiCall.ContentType = "application/json";
apiCall.ContentLength = noBody.Length; //noBody = empty string
Stream c = apiCall.GetRequestStream();
Encoding d = System.Text.Encoding.ASCII;
StreamWriter requestWriter = new StreamWriter(c, d);
requestWriter.Write(noBody);
requestWriter.Close();
WebResponse apiResponse = apiCall.GetResponse(); //This line will return an error.
This will also return the same error:
HttpWebResponse apiResponse = apiCall.GetResponse() as HttpWebResponse;
This will again return the same error:
string status;
using (HttpWebResponse response = apiCall.GetResponse() as HttpWebResponse)
{
status = response.StatusCode.ToString();
}
I just cant seem to correctly call the GetResponse Method.

HttpWebRequest - GetResponse() - WebException ReceiveFailure

I have a WCF service that is running frequent (1000+) outbound connections per minute to external APIs.
My code throws the following exceptions frequently, but not always showing that is is a WebException with the WebException status property being ReceiveFailure
The code that is making the outbound request is the following:
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(paramBuilder.ToString());
request.ServicePoint.ConnectionLeaseTimeout = 0;
request.Method = "GET";
request.Timeout = 33000; //33 Second Timeout Is By Design
Stream stream = default(Stream);
HttpWebResponse response = default(HttpWebResponse);
try
{
response = (HttpWebResponse) request.GetResponse();
stream = response.GetResponseStream();
reader = new StreamReader(stream,Encoding.UTF8);
string str = reader.ReadToEnd();
return str;
}
catch (WebException exception)
{
//Handle WebException
}
catch (Exception exception)
{
//Handle Exception
}
finally
{
if (reader != null)
reader.Dispose();
if (response != null)
response.Close();
if (stream != null)
stream.Dispose();
}
The exception stack trace shows that the exception is caused from GetResponse().
What could be causing this to happen that I receive an occasional WebException -ReceiveFailure.
I have already reference the MSDN documentation for this status, but that doesn't help me.

Shooting in the dark here...
There is a special condition, while waiting for response: if the system clock is being set automatically by the Windows Time service, or manually, you may experience some unpredictable results.
If you're sending your requests over HTTPS, maybe you're facing a regular timeout that was wrongly thrown as a ReceiveFailure.
Check this article for more information: http://support.microsoft.com/kb/2007873

I have a related problem and I realise a few things while I was searching for a solution.
WebExceptionStatus enum is not equivalent to http status code that the API you call returned. Instead it is a enum of possible error that may occour during a http call.
The WebExceptionStatus error code that will be returned when you receive an error (400 to 599) from your API is WebExceptionStatus.ProtocolError aka number 7 as int.
When you need to get the response body or the real http status code returned from the api, first you need to check if WebException.Status is WebExceptionStatus.ProtocolError. Then you can get the real response from WebExceptionStatus.Response and read its content.
Sometimes the timeout is handled by the caller (aka your code) so you do not have a response in that case. So you can look if WebException.Status is WebExceptionStatus.Timeout
This is an example:
try
{
...
}
catch (WebException webException)
{
if (webException.Status == WebExceptionStatus.ProtocolError)
{
var httpResponse = (HttpWebResponse)webException.Response;
var responseText = "";
using (var content = new StreamReader(httpResponse.GetResponseStream()))
{
responseText = content.ReadToEnd(); // Get response body as text
}
int statusCode = (int)httpResponse.StatusCode; // Get the status code
}
else if (webException.Status == WebExceptionStatus.ProtocolError)
{
// Timeout handled by your code. You do not have a response here.
}
// Handle other webException.Status errors. You do not have a response here.
}

.NET service responds 500 internal error and "missing parameter" to HttpWebRequest POSTS but test form works fine

I am using a simple .NET service (asmx) that works fine when invoking via the test form (POST). When invoking via a HttpWebRequest object, I get a WebException "System.Net.WebException: The remote server returned an error: (500) Internal Server Error." Digging deeper, reading the WebException.Response.GetResponseStream() I get the message: "Missing parameter: serviceType." but I've clearly included this parameter.
I'm at a loss here, and its worse that I don't have access to debug the service itself.
Here is the code being used to make the request:
string postData = String.Format("serviceType={0}&SaleID={1}&Zip={2}", request.service, request.saleId, request.postalCode);
byte[] data = (new ASCIIEncoding()).GetBytes(postData);
HttpWebRequest httpWebRequest = (HttpWebRequest)WebRequest.Create(url);
httpWebRequest.Timeout = 60000;
httpWebRequest.Method = "POST";
httpWebRequest.ContentType = "application/x-www-form-urlencoded";
httpWebRequest.ContentLength = data.Length;
using (Stream newStream = httpWebRequest.GetRequestStream())
{
newStream.Write(data, 0, data.Length);
}
try
{
using (response = (HttpWebResponse)httpWebRequest.GetResponse())
{
if (response.StatusCode != HttpStatusCode.OK)
throw new Exception("There was an error with the shipping freight service.");
string responseData;
using (StreamReader responseStream = new StreamReader(httpWebRequest.GetResponse().GetResponseStream(), System.Text.Encoding.GetEncoding("iso-8859-1")))
{
responseData = responseStream.ReadToEnd();
responseStream.Close();
}
if (string.IsNullOrEmpty(responseData))
throw new Exception("There was an error with the shipping freight service. Request went through but response is empty.");
XmlDocument providerResponse = new XmlDocument();
providerResponse.LoadXml(responseData);
return providerResponse;
}
}
catch (WebException webExp)
{
string exMessage = webExp.Message;
if (webExp.Response != null)
{
using (StreamReader responseReader = new StreamReader(webExp.Response.GetResponseStream()))
{
exMessage = responseReader.ReadToEnd();
}
}
throw new Exception(exMessage);
}
Anyone have an idea what could be happening?
Thanks.
UPDATE
Stepping through the debugger, I see the parameters are correct. I also see the parameters are correct in fiddler.
Examining fiddler, I get 2 requests each time this code executes. The first request is a post that sends the parameters. It gets a 301 response code with a "Document Moved Object Moved This document may be found here" message. The second request is a GET to the same URL with no body. It gets a 500 server error with "Missing parameter: serviceType." message.

It seems like you found your problem when you looked at the requests in Fiddler. Taking an excerpt from http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html:
10.3.2 301 Moved Permanently
The requested resource has been assigned a new permanent URI and any future references to this resource SHOULD use one of the returned URIs. Clients with link editing capabilities ought to automatically re-link references to the Request-URI to one or more of the new references returned by the server, where possible.
.....
Note: When automatically redirecting a POST request after
receiving a 301 status code, some existing HTTP/1.0 user agents
will erroneously change it into a GET request.
Here's a couple options that you can take:
Hard-code your program to use the new Url that you see in the 301 response in Fiddler
Adjust your code to retrieve the 301 response, parse out the new Url from the response, and build a new response with the new Url.
The latter option would be ideal if you're dealing with user-based input on the Url (like a web browser), since you don't know where the user is going to want your program to go.