Develop Reference

How can I execute an url call from C# code on a ASP website on a ASCX page?

I need to call a Custom protocol (something like: "custom:signDocs?param1=value?param2=value") that is registered on a client.
I have a working one that is executed via JavaScript on a button click.
But I need to call the url to execute the program I have on the clients pc.
The program is for signing documents and sending them back to the server, and, in the code I have a 15min timer that waits for the status of the documents to change to signed then it shows the documents to the user.
I also tried using webrequest:
//Method that uses the webrequest
{
System.Net.WebRequest.RegisterPrefix("customProtocolName", new PrototipoIDPTRequestCreator());
System.Net.WebRequest req = System.Net.WebRequest.Create(protocolUrlWithParams);
var aux = req.GetResponse();
}
internal class CustomRequestCreator : System.Net.IWebRequestCreate
{
public WebRequest Create(Uri uri)
{
return new CustomWebRequest(uri);
}
}
class CustomWebRequest: WebRequest
{
public override Uri RequestUri { get; }
public CustomWebRequest(Uri uri)
{
RequestUri = uri;
}
}
But this does nothing, I do not know it its even the right path...
Does anyone know of a way to accomplish this?

You can use HttpClient from System.Net.Http like the following example.
Simple get call from a test api endpoint.
using (var client = new HttpClient())
{
client.BaseAddress = new Uri("YOUR_BASE_URL"); //https://localhost:8000
client.DefaultRequestHeaders.Accept.Clear();
client.DefaultRequestHeaders.Accept.Add(
new MediaTypeWithQualityHeaderValue("application/json"));
HttpResponseMessage response = await client.GetAsync("api/test"); //api uri
response.EnsureSuccessStatusCode();
string responseBody = await response.Content.ReadAsStringAsync();
}
Note: For more details refer, HttpClient Doc

.NETCore HttpWebRequest - Old Way isn't Working

Before I upgraded to the newest .NetCore I was able to run the HttpWebRequest, add the headers and content Type and pull the stream of the JSON file from Twitch. Since the upgrade this is not working. I receive a Web Exception each time I go to get the response Stream. Nothing has changed with twitch because it still works with the old Bot. The old code is below:
private const string Url = "https://api.twitch.tv/kraken/streams/channelname";
HttpWebRequest request;
try
{
request = (HttpWebRequest)WebRequest.Create(Url);
}
request.Method = "Get";
request.Timeout = 12000;
request.ContentType = "application/vnd.twitchtv.v5+json";
request.Headers.Add("Client-ID", "ID");
try
{
using (var s = request.GetResponse().GetResponseStream())
{
if (s != null)
using (var sr = new StreamReader(s))
{
}
}
}
I have done some research and found that I may need to start using either an HttpClient or HttpRequestMessage. I have tried going about this but when adding headers content type the program halts and exits. after the first line here: (when using HttpsRequestMessage)
request.Content.Headers.ContentType.MediaType = "application/vnd.twitchtv.v5+json";
request.Content.Headers.Add("Client-ID", "rbp1au0xk85ej6wac9b8s1a1amlsi5");

You are trying to add a ContentType header, but what you really want is to add an Accept header (your request is a GET and ContentType is used only on requests which contain a body, e.g. POST or PUT).
In .NET Core you need to use HttpClient, but remember that to correctly use it you need to leverage the use of async and await.
Here it is an example:
using System.Net.Http;
using System.Net.Http.Headers;
private const string Url = "https://api.twitch.tv/kraken/streams/channelname";
public static async Task<string> GetResponseFromTwitch()
{
using(var client = new HttpClient())
{
client.DefaultRequestHeaders.Accept.Clear();
client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/vnd.twitchtv.v5+json"));
client.DefaultRequestHeaders.Add("Client-ID", "MyId");
using(var response = await client.GetAsync(Url))
{
response.EnsureSuccessStatusCode();
return await response.Content.ReadAsStringAsync(); // here we return the json response, you may parse it
}
}
}

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

Retrieving website content and returning it in ASP.NET MVC 4

I have two servers. One is a private server and I don't want users to have direct access to it, and the other one is the server that public does have access to.
I can access my private server by URL like: http://xxx.xx.xxx.xxx/
What i want to do is create some kind of "proxy", only to work with my private server. My idea is to go to: http://www.domain.com/server/path/here/something
This page should show me the content of http://xxx.xx.xxx.xxx/path/here/something
I have this working, but the only way I could make it work was to return the content as a string, and then the browser would interpret the HTML.
This works fine for pages that return HTML content, but it doesn't work (of course) if I want to access a .gif or any kind of file directly.
Here's the code I currently have:
public string Index(string url)
{
string uri = "http://xxx.xx.xxx.xxx/" + url;
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uri);
request.Method = "GET";
HttpWebResponse response = (HttpWebResponse)request.GetResponse();
StreamReader responseStream = new StreamReader(response.GetResponseStream());
string resultado = responseStream.ReadToEnd();
return resultado;
}
How can I change my code so that it works for any file ?

You can check the response content type and do what you need based on that.
You'll need to change your action to return ActionResult instead of string.
if(response.ContentType.Equals("text/html"))
{
//show html stuff
return Content(resultado);
}
else if(response.ContentType.Contains("image/"))
{
var ms = new MemoryStream();
responseStream.BaseStream.CopyTo(ms);
var imageBytes = ms.ToArray();
return File(imageBytes, response.ContentType);
}

you have to write a system which reads your html or images from resultado and do something according to that PLUS you need to control your Url as well.

How to get the file size from http headers

I want to get the size of an http:/.../file before I download it. The file can be a webpage, image, or a media file. Can this be done with HTTP headers? How do I download just the file HTTP header?

Yes, assuming the HTTP server you're talking to supports/allows this:
public long GetFileSize(string url)
{
long result = -1;
System.Net.WebRequest req = System.Net.WebRequest.Create(url);
req.Method = "HEAD";
using (System.Net.WebResponse resp = req.GetResponse())
{
if (long.TryParse(resp.Headers.Get("Content-Length"), out long ContentLength))
{
result = ContentLength;
}
}
return result;
}
If using the HEAD method is not allowed, or the Content-Length header is not present in the server reply, the only way to determine the size of the content on the server is to download it. Since this is not particularly reliable, most servers will include this information.

Can this be done with HTTP headers?
Yes, this is the way to go. If the information is provided, it's in the header as the Content-Length. Note, however, that this is not necessarily the case.
Downloading only the header can be done using a HEAD request instead of GET. Maybe the following code helps:
HttpWebRequest req = (HttpWebRequest)WebRequest.Create("http://example.com/");
req.Method = "HEAD";
long len;
using(HttpWebResponse resp = (HttpWebResponse)(req.GetResponse()))
{
len = resp.ContentLength;
}
Notice the property for the content length on the HttpWebResponse object – no need to parse the Content-Length header manually.

Note that not every server accepts HTTP HEAD requests. One alternative approach to get the file size is to make an HTTP GET call to the server requesting only a portion of the file to keep the response small and retrieve the file size from the metadata that is returned as part of the response content header.
The standard System.Net.Http.HttpClient can be used to accomplish this. The partial content is requested by setting a byte range on the request message header as:
request.Headers.Range = new RangeHeaderValue(startByte, endByte)
The server responds with a message containing the requested range as well as the entire file size. This information is returned in the response content header (response.Content.Header) with the key "Content-Range".
Here's an example of the content range in the response message content header:
{
"Key": "Content-Range",
"Value": [
"bytes 0-15/2328372"
]
}
In this example the header value implies the response contains bytes 0 to 15 (i.e., 16 bytes total) and the file is 2,328,372 bytes in its entirety.
Here's a sample implementation of this method:
public static class HttpClientExtensions
{
public static async Task<long> GetContentSizeAsync(this System.Net.Http.HttpClient client, string url)
{
using (var request = new System.Net.Http.HttpRequestMessage(System.Net.Http.HttpMethod.Get, url))
{
// In order to keep the response as small as possible, set the requested byte range to [0,0] (i.e., only the first byte)
request.Headers.Range = new System.Net.Http.Headers.RangeHeaderValue(from: 0, to: 0);
using (var response = await client.SendAsync(request))
{
response.EnsureSuccessStatusCode();
if (response.StatusCode != System.Net.HttpStatusCode.PartialContent)
throw new System.Net.WebException($"expected partial content response ({System.Net.HttpStatusCode.PartialContent}), instead received: {response.StatusCode}");
var contentRange = response.Content.Headers.GetValues(#"Content-Range").Single();
var lengthString = System.Text.RegularExpressions.Regex.Match(contentRange, #"(?<=^bytes\s[0-9]+\-[0-9]+/)[0-9]+$").Value;
return long.Parse(lengthString);
}
}
}
}

WebClient webClient = new WebClient();
webClient.OpenRead("http://stackoverflow.com/robots.txt");
long totalSizeBytes= Convert.ToInt64(webClient.ResponseHeaders["Content-Length"]);
Console.WriteLine((totalSizeBytes));

HttpClient client = new HttpClient(
new HttpClientHandler() {
Proxy = null, UseProxy = false
} // removes the delay getting a response from the server, if you not use Proxy
);
public async Task<long?> GetContentSizeAsync(string url) {
using (HttpResponseMessage responce = await client.GetAsync(url))
return responce.Content.Headers.ContentLength;
}