Develop Reference

GDax API GET request always returns Error 400

I'm trying to get the order book from GDAX (link to documentation of the call) but when doing it from the c# executable I always get Error 400 - Bad request.
When taking the actual URL and pasting it into my browser, it works fine.
String URL = "https://api.gdax.com/products/BTC-USD/book?level=2";
WebRequest request = WebRequest.Create(URL);
WebResponse response = request.GetResponse();

The actual issue with your API call is , the API is expecting a user-agent string while making the request: Below is the code in working condition:
try
{
String URL = "http://api.gdax.com/products/BTC-USD/book?level=2";
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(URL);
request.UserAgent = ".NET Framework Test Client";
HttpWebResponse response = (HttpWebResponse)request.GetResponse();
var encoding = ASCIIEncoding.ASCII;
using (var reader = new System.IO.StreamReader(response.GetResponseStream(), encoding))
{
string responseText = reader.ReadToEnd();
}
}
catch(WebException ex)
{
HttpWebResponse xyz = ex.Response as HttpWebResponse;
var encoding = ASCIIEncoding.ASCII;
using (var reader = new System.IO.StreamReader(xyz.GetResponseStream(), encoding))
{
string responseText = reader.ReadToEnd();
}
}
Basically ProtocolError indicates that you have received the response but there is an error related to protocol, which you can observe, when you read the response content from exception. I have added catch to handle the exception and read ex.Response (which is HttpWebResponse) and could see that the API is asking for user-agent to be suppllied while making the call. I got to see the error as "{"message":"User-Agent header is required."}"
You can ignore the code inside the exception block, I used it only to see what is the actual response message, which contains actual error details
Note: I have boxed WebRequest to HttpWebRequest to have additional http protocol related properties and most importantly "UserAgent" property which is not available with the WebRequest class.

You need to Accept the certificarte, Google for access to a https webrequest.
Like this

Passing body content when calling a Delete Web API method using System.Net.Http

I have a scenario where I need to call my Web API Delete method constructed like the following:
// DELETE: api/products/{id}/headers
[HttpDelete("{id}/headers")]
public void DeleteProductHeaders(int id, [FromBody] string query)
{
}
The trick is that in order to get the query over I need to send it through the body and DeleteAsync does not have a param for json like post does. Does anyone know how I can do this using System.Net.Http client in c#?
// Delete a product's headers
public void DeleteProductHeaders(int id, string query)
{
using (var client = GetClient())
{
HttpResponseMessage response;
try
{
// HTTP DELETE
response = client.DeleteAsync($"api/products/{id}/headers").Result;
}
catch (Exception ex)
{
throw new Exception("Unable to connect to the server", ex);
}
}
return retVal;
}

Here is how I accomplished it
var request = new HttpRequestMessage(HttpMethod.Delete, "http://www.example.com/");
request.Content = new StringContent(JsonConvert.SerializeObject(object), Encoding.UTF8, "application/json");
await this.client.SendAsync(request);

I think the reason HttpClient is designed that way is although HTTP 1.1 spec allows message body on DELETE requests, essentially it is not expected to do so as the spec doesn't define any semantics for it as it is defined here. HttpClient strictly follows HTTP spec thus you see it doesn't allow you to add a message body to the request.
So, I think your option from the client side includes using HttpRequestMessage described in here. If you want to fix it from the backend and if your message body would work well in query params you can try that instead of sending the query in message body.
I personally think DELETE should be allowed to have a message body and should not be ignored in a server as there are certainly use cases for that like the one you mentioned here.
In any case for more productive discussion on this please have a look at this.

My API as below:
// DELETE api/values
public void Delete([FromBody]string value)
{
}
Calling from C# server side
string URL = "http://localhost:xxxxx/api/values";
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(URL);
request.Method = "DELETE";
request.ContentType = "application/json";
string data = Newtonsoft.Json.JsonConvert.SerializeObject("your body parameter value");
request.ContentLength = data.Length;
StreamWriter requestWriter = new StreamWriter(request.GetRequestStream(), System.Text.Encoding.ASCII);
requestWriter.Write(data);
requestWriter.Close();
try
{
WebResponse webResponse = request.GetResponse();
Stream webStream = webResponse.GetResponseStream();
StreamReader responseReader = new StreamReader(webStream);
string response = responseReader.ReadToEnd();
responseReader.Close();
}
catch
{
}

Getting the Redirected URLs from the Original URL [duplicate]

Using the WebClient class I can get the title of a website easily enough:
WebClient x = new WebClient();
string source = x.DownloadString(s);
string title = Regex.Match(source,
#"\<title\b[^>]*\>\s*(?<Title>[\s\S]*?)\</title\>",
RegexOptions.IgnoreCase).Groups["Title"].Value;
I want to store the URL and the page title. However when following a link such as:
http://tinyurl.com/dbysxp
I'm clearly going to want to get the Url I'm redirected to.
QUESTIONS
Is there a way to do this using the WebClient class?
How would I do it using HttpResponse and HttpRequest?

If I understand the question, it's much easier than people are saying - if you want to let WebClient do all the nuts and bolts of the request (including the redirection), but then get the actual response URI at the end, you can subclass WebClient like this:
class MyWebClient : WebClient
{
Uri _responseUri;
public Uri ResponseUri
{
get { return _responseUri; }
}
protected override WebResponse GetWebResponse(WebRequest request)
{
WebResponse response = base.GetWebResponse(request);
_responseUri = response.ResponseUri;
return response;
}
}
Just use MyWebClient everywhere you would have used WebClient. After you've made whatever WebClient call you needed to do, then you can just use ResponseUri to get the actual redirected URI. You'd need to add a similar override for GetWebResponse(WebRequest request, IAsyncResult result) too, if you were using the async stuff.

I know this is already an answered question, but this works pretty to me:
HttpWebRequest request = (HttpWebRequest)WebRequest.Create("http://tinyurl.com/dbysxp");
request.AllowAutoRedirect = false;
HttpWebResponse response = (HttpWebResponse)request.GetResponse();
string redirUrl = response.Headers["Location"];
response.Close();
//Show the redirected url
MessageBox.Show("You're being redirected to: "+redirUrl);
Cheers.! ;)

With an HttpWebRequest, you would set the AllowAutoRedirect property to false. When this happens, any response with a status code between 300-399 will not be automatically redirected.
You can then get the new url from the response headers and then create a new HttpWebRequest instance to the new url.
With the WebClient class, I doubt you can change it out-of-the-box so that it does not allow redirects. What you could do is derive a class from the WebClient class and then override the GetWebRequest and the GetWebResponse methods to alter the WebRequest/WebResponse instances that the base implementation returns; if it is an HttpWebRequest, then set the AllowAutoRedirect property to false. On the response, if the status code is in the range of 300-399, then issue a new request.
However, I don't know that you can issue a new request from within the GetWebRequest/GetWebResponse methods, so it might be better to just have a loop that executes with HttpWebRequest/HttpWebResponse until all the redirects are followed.

I got the Uri for the redirected page and the page contents.
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(strUrl);
request.AllowAutoRedirect = true;
HttpWebResponse response = (HttpWebResponse)request.GetResponse();
Stream dataStream = response.GetResponseStream();
strLastRedirect = response.ResponseUri.ToString();
StreamReader reader = new StreamReader(dataStream);
string strResponse = reader.ReadToEnd();
response.Close();

In case you are only interested in the redirect URI you can use this code:
public static string GetRedirectUrl(string url)
{
HttpWebRequest request = (HttpWebRequest) HttpWebRequest.Create(url);
request.AllowAutoRedirect = false;
using (HttpWebResponse response = HttpWebResponse)request.GetResponse())
{
return response.Headers["Location"];
}
}
The method will return
null - in case of no redirect
a relative url - in case of a redirect
Please note: The using statement (or a final response.close()) is essential. See MSDN Library for details. Otherwise you may run out of connections or get a timeout when executing this code multiple times.

HttpWebRequest.AllowAutoRedirect can be set to false. Then you'd have to manually http status codes in the 300 range.
// Create a new HttpWebRequest Object to the mentioned URL.
HttpWebRequest myHttpWebRequest=(HttpWebRequest)WebRequest.Create("http://www.contoso.com");
myHttpWebRequest.MaximumAutomaticRedirections=1;
myHttpWebRequest.AllowAutoRedirect=true;
HttpWebResponse myHttpWebResponse=(HttpWebResponse)myHttpWebRequest.GetResponse();

The WebClient class has an option to follow redirects. Set that option and you should be fine.

Ok this is really hackish, but the key is to use the HttpWebRequest and then set the AllowAutoRedirect property to true.
Here's a VERY hacked together example
HttpWebRequest req = (HttpWebRequest)WebRequest.Create("http://tinyurl.com/dbysxp");
req.Method = "GET";
req.AllowAutoRedirect = true;
WebResponse response = req.GetResponse();
response.GetResponseStream();
Stream responseStream = response.GetResponseStream();
// Content-Length header is not trustable, but makes a good hint.
// Responses longer than int size will throw an exception here!
int length = (int)response.ContentLength;
const int bufSizeMax = 65536; // max read buffer size conserves memory
const int bufSizeMin = 8192; // min size prevents numerous small reads
// Use Content-Length if between bufSizeMax and bufSizeMin
int bufSize = bufSizeMin;
if (length > bufSize)
bufSize = length > bufSizeMax ? bufSizeMax : length;
StringBuilder sb;
// Allocate buffer and StringBuilder for reading response
byte[] buf = new byte[bufSize];
sb = new StringBuilder(bufSize);
// Read response stream until end
while ((length = responseStream.Read(buf, 0, buf.Length)) != 0)
sb.Append(Encoding.UTF8.GetString(buf, 0, length));
string source = sb.ToString();string title = Regex.Match(source,
#"\<title\b[^>]*\>\s*(?<Title>[\s\S]*?)\</title\>",RegexOptions.IgnoreCase).Groups["Title"].Value;
enter code here

Request parameter in Windows Mobile for REST API's

I have one Windows Handheld device application on .Net framework 3.5 which has the requirement of accessing a REST API. The REST API gives me JSON output which I am going to process later. I have the following code for that:-
HttpWebRequest webRequest;
string result = String.Empty;
try
{
webRequest = (HttpWebRequest)WebRequest.Create(url);
webRequest.Method = "POST";
webRequest.KeepAlive = false;
webRequest.ContentType = "application/x-www-form-urlencoded";
using (WebResponse response = webRequest.GetResponse())
{
using (StreamReader streamReader = new StreamReader(response.GetResponseStream()))
{
result = streamReader.ReadToEnd();
}
}
}
catch (Exception ex)
{
result = ex.Message;
}
The url variable is holding the url for the API with some query parameters in it.
For Example "http://www.something.com/Login?id=test&pwd=test".
Now my problem is I dont want to use the query string parameters rather I want to use Request parameters because the above approach does not work every time perfectly. Some times I get an "Unauthorized" error. And also I have one tokenId which I need to send everytime I am calling the API and the token Id is in base64 format.
Can anyone please help me how can I use the Request Parameter feature to send the parameter values?

use the Headers property of your request object.
webRequest.Headers.Add("id", "test");
webRequest.Headers.Add("pwd", "test");
webRequest.Headers.Add("token", myToken);

Invoking a URL - c#

I m trying to invoke a URL in C#, I am just interested in invoking, and dont care about response. When i have the following, does it mean that I m invoking the URL?
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);

You need to actually perform the request:
var request = (HttpWebRequest)WebRequest.Create(url);
request.GetResponse();
The call to GetResponse makes the outbound call to the server. You can discard the response if you don't care about it.

First) Create WebRequest to execute URL.
Second) Use WebResponse to get response.
Finally) Use StreamReader to decode response and convert it to normal string.
string url = "Your request url";
WebRequest request = HttpWebRequest.Create(url);
WebResponse response = request.GetResponse();
StreamReader reader = new StreamReader(response.GetResponseStream());
string responseText = reader.ReadToEnd();

You can use this:
string address = "http://www.yoursite.com/page.aspx";
using (WebClient client = new WebClient())
{
client.DownloadString(address);
}

No when you say request.GetResponse(); then you invoke it.

Probably not. See: http://www.codeproject.com/KB/webservices/HttpWebRequest_Response.aspx
You're allowed to set the Method, ContentType, etc., all which would have to be done before the request is actually sent. It looks like GetResponse() actually sends the request. You can simply ignore the return value.