I'm doing research into web programming in ASP .NET and came across these two classes. I was wondering what might these be used for?
My first thought is that they could be used if you were setting up a proxy between the client and server, but I'm not sure if this is the main purpose or not.
Thanks
edit: classes not methods
They can indeed be used for that. This isn't specific to ASP.NET however.
You can create a HttpWebRequest object by doing:
HttpWebRequest request = (HttpWebRequest)WebRequest.Create("http://url.com");
And you invoke it to retrieve an HttpWebResponse:
HttpWebResponse response = (HttpWebResponse)request.GetResponse();
There's a lot of customization you can do here, but hopefully this will give you a starting point for reading data off the web.
As their names imply, these are classes to either create a request (HttpWebRequest) or create a response (HttpWebResponse).
Using HttpWebRequest you define a request to a URI using the HTTP-protocol. Whereas the HttpWebResponse class delivers you an answer of an HTTP-server providing all the information like HTTP-headers and actual body of the request.
This is an example from MSDN
HttpWebRequest HttpWReq =
(HttpWebRequest)WebRequest.Create("http://www.contoso.com");
HttpWebResponse HttpWResp = (HttpWebResponse)HttpWReq.GetResponse();
// Insert code that uses the response object.
HttpWResp.Close();
Consider the casting from the base-class WebRequest.
See HttpWebRequest and HttpWebResponse.
They are used for communicating with another process using the HTTP protocol.
In the context of ASP.NET, your process could use them to talk to another service. Maybe your database uses the HTTP protocol, such as CouchDB. Perhaps you have a rest service that your ASP.NET application needs to talk to.
Related
I am building an application with C# and one of the requirements is that the headers have to contain very specific data. I have been working with the WebClient and HttpWebRequest classes in C# but both do not have the option to explicitly remove the Connection header. This is what I have tried:
WebClient
client.Headers.Remove("Connection");
client.Headers.Add("Connection", null); // if only...
HttpWebRequest
request.Connection = null;
request.Connection = "";
Some of what I have read is that you can only have this header set to Keep-Alive or Close. I need it to not even be on the web request.
All other required headers are adding just fine. It is this one that is causing a head ache. I'm beginning to believe that removing the Connection header is not possible. Is there any language where it is possible if this is the case?
Much appreciation for the time you guys take to look at this!
Thank you!
I'm not quite sure how to remove that specific header, but you could try using the HttpClient class instead of HttpWebRequest or WebClient.
HttpClient class
This class is more up-to-date way of executing HTTP requests in C#
I can use both HttpWebRequest to send an HTTP request and get an HTTP response without a WebClient.
When should you use HttpWebRequest and when should you use WebClient?
WebClient can be used when you don't need any fine-tuning.
When using HttpWebRequest, you can control various options, including timeouts (very important). So basically - WebClient for toy projects / POCs, HttpWebRequest for actual business.
Personally I always use WebClient. The API seems more simple. It uses HttpWebRequest under the covers.
WebClient is ideal for downloads and uploads.
HttpWebRequest is ideal for web connections, including sending HTTP POST requests, as seen here: HTTP request with post
If you do not need access to the underlying stream but are just uploading or downloading "data", i.e. a file some bytes or a string, WebClient is a simplifying abstraction.
I am new to web services. I am dealing with testing APIs in my project. In the previous version the company used GET and POST methods but not PUT and DELETE methods. For the HTTP DELETE method, I have browsed various websites where I found the example code snippets for GET and POST methods, but not for DELETE and PUT methods (why?).
Can anyone give me an example code snippet (C#) for RESTful HTTP DELETE method and explain how to call the DELETE request?
Check out the following code snippet:
string sURL = "<HERE GOES YOUR URL>";
WebRequest request = WebRequest.Create(sURL);
request.Method = "DELETE";
HttpWebResponse response = (HttpWebResponse)request.GetResponse();
In the response object you should check the StatusCode property (it should be 200 or 204 if everything goes right, see here for more info).
I'm narrowing in on an underlying problem related to two prior questions.
Basically, I've got a URL that when I fetch it manually (paste it into browser) works just fine, but when I run through some code (using the HttpWebRequest) has a different result.
The URL (example):
http://208.106.250.207:8192/announce?info_hash=-%CA8%C1%C9rDb%ADL%ED%B4%2A%15i%80Z%B8%F%C&peer_id=01234567890123456789&port=6881&uploaded=0&downloaded=0&left=0&compact=0&no_peer_id=0&event=started
The code:
String uri = BuildURI(); //Returns the above URL
HttpWebRequest req = (HttpWebRequest)HttpWebRequest.Create(uri);
req.Proxy = new WebProxy();
WebResponse resp = req.GetResponse();
Stream stream = resp.GetResponseStream();
... Parse the result (which is an error message from the server claiming the url is incorrect) ...
So, how can I GET from a server given a URL? I'm obviously doing something wrong here, but can't tell what.
Either a fix for my code, or an alternative approach that actually works would be fine. I'm not wed at all to the HttpWebRequest method.
I recommend you use Fiddler to trace both the "paste in web browser" call and the HttpWebRequest call.
Once traced you will be able to see any differences between them, whether they are differences in the request url, in the form headers, etc, etc.
It may actually be worth pasting the raw requests from both (obtained from Fiddler) here, if you can't see anything obvious.
Well, the only they might differ is in the HTTP headers that get transmitted. In particular the User-Agent.
Also, why are you using a WebProxy? That is not really necessary and it most likely is not used by your browser.
The rest of your code is fine.. Just make sure you set up the HTTP headers correctly. Check this link out:
I would suggest that you get yourself a copy of WireShark and examine the communication that happens between your browser and the server that you are trying to access. Doing so will be rather trivial using WireShark and it will show you the exact HTTP message that is being sent from the browser.
Then take a look at the communication that goes on between your C# application and the server (again using WireShark) and then compare the two to find out what exactly is different.
If the communication is a pure HTTP GET method (i.e. there is no HTTP message body involved), and the URL is correct then the only two things I could think of are:
make sure that your are send the right protocol (i.e. HTTP/1.0 or HTTP/1.1 or whatever it is that you should be sending)
make sure that you are sending all required HTTP headers correctly, and obviously that you are not sending any HTTP headers that you shouldn't be sending.
There could be something wrong with the URL. Instead of using a string, it's usually better to use an instance of System.Uri:
String url = BuildURI(); //Returns the above URL
Uri uri = new Uri(url);
HttpWebRequest req = (HttpWebRequest)HttpWebRequest.Create(url);
req.Proxy = new WebProxy();
using (WebResponse resp = req.GetResponse()) {
using (Stream stream = resp.GetResponseStream()) {
// whatever
}
}
I think you need to see exactly what's flowing to your server in the HTTP request. Does sound likely that the headers are interestingly different.
You can introduce a some kind of debugging proxy between your request and the server (for example RAD has such a capability in the box).
I'm writing a small tool in C# which will need to send and receive data to/from a website using POST and json formatting. I've never done anything like this before in C# (or any language really) so I'm struggling to find some useful information to get me started.
I've found some information on the WebRequest class in C# (specifically from here) but before I start diving into it, I wondered if this was the right tool for the job.
I've found plenty of tools to convert data into the json format but not much else, so any information would be really helpful here in case I end up down a dead end.
WebRequest and more specifically the HttpWebRequest class is a good starting point for what you want to achieve. To create the request you will use the WebRequest.Create and cast the created request to an HttpWebRequest to actually use it. You will then create your post data and send it to the stream like:
HttpWebRequest req = (HttpWebRequest)
WebRequest.Create("http://mysite.com/index.php");
req.Method = "POST";
req.ContentType = "application/x-www-form-urlencoded";
string postData = "var=value1&var2=value2";
req.ContentLength = postData.Length;
StreamWriter stOut = new
StreamWriter(req.GetRequestStream(),
System.Text.Encoding.ASCII);
stOut.Write(postData);
stOut.Close();
Similarly you can read the response back by using the GetResponse method which will allow you to read the resultant response stream and do whatever else you need to do. You can find more info on the class at:
http://msdn.microsoft.com/en-us/library/system.net.httpwebrequest.aspx
WebClient is sometimes easier to use than WebRequest. You may want to take a look at it.
For JSON deserialization you are going to want to look at the JavaScriptSerializer class.
WebClient example:
using (WebClient client = new WebClient ())
{
//manipulate request headers (optional)
client.Headers.Add (HttpRequestHeader.UserAgent, "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.2; .NET CLR 1.0.3705;)");
//execute request and read response as string to console
using (StreamReader reader = new StreamReader(client.OpenRead(targetUri)))
{
string s = reader.ReadToEnd ();
Console.WriteLine (s);
}
}
Marked as wiki in case someone wants to update the code
When it comes to POSTing data to a web site, System.Net.HttpWebRequest (the HTTP-specific implementation of WebRequest) is a perfectly decent solution. It supports SSL, async requests and a bunch of other goodies, and is well-documented on MSDN.
The payload can be anything: data in JSON format or whatever -- as long as you set the ContentType property to something the server expects and understands (most likely application/json, text/json or text/x-json), all will be fine.
One potential issue when using HttpWebRequest from a system service: since it uses the IE proxy and credential information, default behavior may be a bit strange when running as the LOCALSYSTEM user (or basically any account that doesn't log on interactively on a regular basis). Setting the Proxy and Authentication properties to Nothing (or, as you C# folks prefer to call it, null, I guess) should avoid that.
I have used WebRequest for interacting with websites. It is the right 'tool'
I can't comment on the JSON aspect of your question.
The currently highest rated answer is helpful, but it doesn't send or receive JSON.
Here is an example that uses JSON for both sending and receiving:
How to post json object in web service
And here is the StackOverflow question that helped me most to solve this problem:
Problems sending and receiving JSON between ASP.net web service and ASP.Net web client
And here is another related question:
json call with C#
To convert from instance object to json formatted string and vice-versa, try out Json.NET:
http://json.codeplex.com/
I am currently using it for a project and it's easy to learn and work with and offers some flexibility in terms of serializing and custom type converters. It also supports a LINQ syntax for querying json input.
in 3.5 there is a built-in jsonserializer. The webrequest is the right class your looking for.
A few examples:
Link
http://dev.aol.com/blog/markdeveloper/ShareFileWithNETFramework
Link