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Translating this to a HTTP POST in C#

I am currently experimenting with the HTTP request. I have successfully managed to do get requests and I have read on doing post request with HTTP request.
Now I am trying to work with the yahoo API and in order to use the Yahoo api it states that at
The Message Management API can be used to send a message to another
Yahoo! Messenger contact. The API is very simple to use, as shown
here. Note that the contact that the message is sent to is part of the
URI, using the following format:<server>/v1/message/<network>/<contactID>
POST /v1/message/yahoo/targetYahooId?sid=msgrsessionid
Host: rcore1.messenger.yahooapis.com
Authorization: < Standard OAuth credentials >
Content-Type: application/json;charset=utf-8
Content-Length: 25
{
"message" : "Hey there"
}
Now I have an OAuth string which I obtained from get using the HttpWebRequest object.
The string is something like this
oauth_token=A%3Dvh....aRg--&oauth_token_secret=bd46a....c9239&oauth_expires_in=3600&oauth_session_handle=ALtT.....3J1N4Zg--&oauth_authorization_expires_in=784964948&xoauth_yahoo_guid=TUSKED5...NCIA
UPDATE
Now my question are as follows :
1- If I am using WebRequest object in C# what would my URI look like
2- I understand that it requires a JSON type object. How do i even know what OAuth parameters are ?

One thing you'll need to change is the content type:
request.ContentType = "application/json;charset=utf-8";
And of course, the url.

you need to change the url on the line with the url in it
you need to change the content-type line
you need to make the payload into a json string then convert it to a byte array (byteArray in the sample)
either assemble the json by hand "{ foo:'bar'}" etc or use json.net
and set the content-length

Looks like it's expecting a JSON object for the request body. Depending on the version of .NET you're using, you can either use a Javascript serializer as shown here (https://stackoverflow.com/a/7003815/939080) or JSON.NET (http://james.newtonking.com/projects/json-net.aspx) to convert your form collection into JSON output.

You are asking an open-ended question that would require people to write a bunch of code for you if you want a specific and complete answer. As others have pointed out, there are several issues that you'd need to deal with:
The JSON payload, which would be a straightforward matter of putting the JSON string in the request body via the byteArray used in the code sample.
The content type, which you would need to change as described by jrummell.
The OAuth credentials, which is a kettle of fish you'll need to read about, understand, and acquire a library for. Here's a good place to start looking for a library.

Why is my S3 pre-signed request invalid when I set a response header override that contains a "+"?

I'm using the Amazon .NET SDK to generate a pre-signed URL like this:
public System.Web.Mvc.ActionResult AsActionResult(string contentType, string contentDisposition)
{
ResponseHeaderOverrides headerOverrides = new ResponseHeaderOverrides();
headerOverrides.ContentType = contentType;
if (!string.IsNullOrWhiteSpace(contentDisposition))
{
headerOverrides.ContentDisposition = contentDisposition;
}
GetPreSignedUrlRequest request = new GetPreSignedUrlRequest()
.WithBucketName(bucketName)
.WithKey(objectKey)
.WithProtocol(Protocol.HTTPS)
.WithExpires(DateTime.Now.AddMinutes(6))
.WithResponseHeaderOverrides(headerOverrides);
string url = S3Client.GetPreSignedURL(request);
return new RedirectResult(url, permanent: false);
}
This works perfectly, except if my contentType contains a + in it. This happens when I try to get an SVG file, for example, which gets a content type of image/svg+xml. In this case, S3 throws a SignatureDoesNotMatch error.
The error message shows the StringToSign like this:
GET 1234567890 /blah/blabh/blah.svg?response-content-disposition=filename="blah.svg"&response-content-type=image/svg xml
Notice there's a space in the response-content-type, where it now says image/svg xml instead of image/svg+xml. It seems to me like that's what is causing the problem, but what's the right way to fix it?
Should I be encoding my content type? Enclose it within quotes or something? The documentation doesn't say anything about this.

Update
This bug has been fixed as of Version 1.4.1.0 of the SDK.
Workaround
This is a confirmed bug in the AWS SDK, so until they issue a fix I'm going with this hack to make things work:
Specify the content type exactly how you want it to look like in the response header. So, if you want S3 to return a content type of image/svg+xml, set it exactly like this:
ResponseHeaderOverrides headerOverrides = new ResponseHeaderOverrides();
headerOverrides.ContentType = "image/svg+xml";
Now, go ahead and generate the pre signed request as usual:
GetPreSignedUrlRequest request = new GetPreSignedUrlRequest()
.WithBucketName(bucketName)
.WithKey(objectKey)
.WithProtocol(Protocol.HTTPS)
.WithExpires(DateTime.Now.AddMinutes(6))
.WithResponseHeaderOverrides(headerOverrides);
string url = S3Client.GetPreSignedURL(request);
Finally, "fix" the resulting URL with the properly URL encoded value for your content type:
url = url.Replace(contentType, HttpUtility.UrlEncode(contentType));
Yes, it's a dirty workaround but, hey, it works for me! :)

Strange indeed - I've been able reproduce this easily, with the following observed behavior:
replacing + in the the URL generated by GetPreSignedURL() with its encoded form %2B yields a working URL/signature
this holds true, no matter whether / is replaced with its encoded form %2F or not
encoding the contentType upfront before calling GetPreSignedURL(), e.g. via the HttpUtility.UrlEncode Method, yields invalid signatures regardless of any variation of the generated URL
Given how long this functionality is available already, this is somewhat surprising, but I'd still consider it to be a bug - accordingly it might be best to inquiry about this in the Amazon Simple Storage Service forum.
Update: I just realized you asked the same question there already and the bug got confirmed indeed, so the correct answer can be figured out over time by monitoring the AWS team response ;)
Update: This bug has been fixed as of Version 1.4.1.0 of the SDK.

wampserver (PHP), where is the first time that the $_POST varibale is being set?

My $_POST is empty (at the server) when I'm trying to post at other content type like application/octet-stream, or when i'm using WebClient method at my c# code (for sending a binary 8bit row data).
The server works fine for regular string and only for ContentType = "application/x-www-form-urlencoded".
Where can I check the variale $_POST? at the Request class?

To get raw POST data, use:
$data = file_get_contents("php://input");

How is an image served from a URL with an ASPX extension?

Can Somebody tell how to create such kind of urls
for example if you see the url
http://office.microsoft.com/global/images/default.aspx?assetid=ZA103873861033
you will redirect to an image ..
my question is , though this url is an image..its extension is aspx..how is it possible.
how to create such kind of url's
Thanks

This is a common method for displaying an image that's stored as a binary object in a database. One tutorial, among many, can be found here.
Essentially, what they're doing is using the aspx page to accept the URL parameter which tells them what image to fetch from the database. Then in the response they clear all output and headers, set the headers for the image, write the binary data to the response stream, and close the response stream.
So it's not really "redirecting" you to an image. The "page" being requested turns out to be an image resource in the response.

By setting the ContentType in the response from the server
HttpContext.Response.ContentType = "image/jpeg";

easiest way is to add generic handler *.ashx and in ashx file u'll have code behind which u can get querystring and manipulate response eg. Response.WriteFile(...)

File extensions literally have no meaning on the WWW. The thing that correctly describes the content at a particular URL is the content-type/MIME-type. This is delivered in an HTTP header when the URL is requested prior to delivery of the main HTTP payload. Other answers describe how you might correctly set this in ASP.NET.

Aside from all other answers they may be doing a Server.Transfer() (so that you don't see it client-side) to the image file. This still means the response headers are being set to the appropriate MIME type but it also means the image isn't necesarilly coming from a database. This technique can be used to hide the actual image URL in attempts to prevent hotlinking.

HTTP Post in C# console app doesn't return the same thing as a browser request

I have a C# console app (.NET 2.0 framework) that does an HTTP post using the following code:
StringBuilder postData = new StringBuilder(100);
postData.Append("post.php?");
postData.Append("Key1=");
postData.Append(val1);
postData.Append("&Key2=");
postData.Append(val2);
byte[] dataArray = Encoding.UTF8.GetBytes(postData.ToString());
HttpWebRequest httpRequest = (HttpWebRequest)WebRequest.Create("http://example.com/");
httpRequest.Method = "POST";
httpRequest.ContentType = "application/x-www-form-urlencoded";
httpRequest.ContentLength = dataArray.Length;
Stream requestStream = httpRequest.GetRequestStream();
requestStream.Write(dataArray, 0, dataArray.Length);
requestStream.Flush();
requestStream.Close();
HttpWebResponse webResponse = (HttpWebResponse)httpRequest.GetResponse();
if (httpRequest.HaveResponse == true) {
Stream responseStream = webResponse.GetResponseStream();
StreamReader responseReader = new System.IO.StreamReader(responseStream, Encoding.UTF8);
String responseString = responseReader.ReadToEnd();
}
The outputs from this are:
webResponse.ContentLength = -1
webResponse.ContentType = text/html
webResponse.ContentEncoding is blank
The responseString is HTML with a title and body.
However, if I post the same URL into a browser (http://example.com/post.php?Key1=some_value&Key2=some_other_value), I get a small XML snippet like:
<?xml version="1.0" ?>
<RESPONSE RESULT="SUCCESS"/>
with none of the same HTML as in the application. Why are the responses so different? I need to parse the returned result which I am not getting in the HTML. Do I have to change how I do the post in the application? I don't have control over the server side code that accepts the post.

If you are indeed supposed to use the POST HTTP method, you have a couple things wrong. First, this line:
postData.Append("post.php?");
is incorrect. You want to post to post.php, you don't want post the value "post.php?" to the page. Just remove this line entirely.
This piece:
... WebRequest.Create("http://example.com/");
needs post.php added to it, so...
... WebRequest.Create("http://example.com/post.php");
Again this is assuming you are actually supposed to be POSTing to the specified page instead of GETing. If you are supposed to be using GET, then the other answers already supplied apply.

You'll want to get an HTTP sniffer tool like Fiddler and compare the headers that are being sent from your app to the ones being sent by the browser. There will be something different that is causing the server to return a different response. When you tweak your app to send the same thing browser is sending you should get the same response. (It could be user-agent, cookies, anything, but something is surely different.)

I've seen this in the past.
When you run from a browser, the "User-Agent" in the header is "Mozilla ...".
When you run from a program, it's different and generally specific to the language used.

I think you need to use a GET request, instead of POST. If the url you're using has querystring values (like ?Key1=some_value&Key2=some_other_value) then it's expecting a GET. Instead of adding post values to your webrequest, just put this data in the querystring.
HttpWebRequest httpRequest = (HttpWebRequest)WebRequest.Create("http://example.com/?val1=" + val1 + "&val2=" + val2);
httpRequest.Method = "GET";
httpRequest.ContentType = "application/x-www-form-urlencoded";
....
So, the result you're getting is different when you POST the data from your app because the server-side code has a different output when it can't read the data it's expecting in the querystring.

In your code you a specify the POST method which sends the data to the PHP file without putting the data in the web address. When you put the information in the address bar, that is not the POST method, that is the GET method. The name may be confusing, but GET just means that the data is being sent to the PHP file through the web address, instead of behind the scenes, not that it is supposed to get any information. When you put the address in the browser it is using a GET.
Create a simple html form and specify POST as the method and your url as the action. You will see that the information is sent without appearing in the address bar.
Then do the same thing but specify GET. You will see the information you sent in the address bar.

I believe the problem has something to do with the way your headers are set up for the WebRequest.
I have seen strange cases where attempting to simulate a browser by changing headers in the request makes a difference to the server.
The short answer is that your console application is not a web browser and the web server of example.com is expecting to interact with a browser.
You might also consider changing the ContentType to be "multipart/form-data".
What I find odd is that you are essentially posting nothing. The work is being done by the query string. Therefore, you probably should be using a GET instead of a POST.

Is the form expecting a cookie? That is another possible reason why it works in the browser and not from the console app.