i want check file in subdomain at another subdomain, file in sub1 and i want check this file in sub2.
address file in sub1: sub1.mysite.com/img/10.jpg and
Server.MapPath(#"~/img/10.jpg");
i have check this file in sub2, so i use this code: some code here it's
if (System.IO.File.Exists(Server.MapPath(#"~/img/10.jpg")))
{
...
}
if (System.IO.File.Exists("http://sub1.mysite.com/img/10.jpg"))
{
...
}
but its not working. please help me.
You'll have to access it via HTTP using HttpWebRequest. You could create a utility method to do this, something like:
public static bool CheckExists(string url)
{
Uri uri = new Uri(url);
if (uri.IsFile) // File is local
return System.IO.File.Exists(uri.LocalPath);
try
{
HttpWebRequest request = WebRequest.Create(uri) as HttpWebRequest;
request.Method = "HEAD"; // No need to download the whole thing
HttpWebResponse response = request.GetResponse() as HttpWebResponse;
return (response.StatusCode == HttpStatusCode.OK); // Return true if the file exists
}
catch
{
return false; // URL does not exist
}
}
And then call it like:
if(CheckExists("http://sub1.mysite.com/img/10.jpg"))
{
...
}
Use HttpWebRequest to send request for resource and inspect the response.
Something like:
bool fileExists = false;
try
{
HttpWebRequest request = (HttpWebRequest)System.Net.WebRequest.Create("http://sub1.mysite.com/img/10.jpg");
using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
{
fileExists = (response.StatusCode == HttpStatusCode.OK);
}
}
catch
{
}
In a web application I have to first check if an image exists and then display this image or a dummy image.
I use the following code and it works for URLS like:
"http://www.somedomain.com/niceimage.png"
"https://www.somedomain.com/niceimage.png".
public virtual bool WebResourceExists(string url)
{
WebHeaderCollection headers = null;
WebResponse response = null;
try
{
WebRequest request = WebRequest.Create(url);
request.Method = "HEAD";
response = request.GetResponse();
headers = response.Headers;
bool result = int.Parse(headers["Content-Length"]) > 0;
return result;
}
catch (System.Net.WebException)
{
return false;
}
catch (Exception e)
{
_log.Error(e);
return false;
}
finally
{
if (response != null)
{
response.Close();
}
}
}
In some places the the method is called with protocol agnostic urls like "//www.somedomain.com/niceimage.png".
There is an exception thrown for such urls:
System.InvalidCastException: Unable to cast object of type
'System.Net.FileWebRequest' to type 'System.Net.HttpWebRequest'
Is there a way to use protocol agnostic urls other then just prepending "http:" to the url?
Protocol-agnostic URLs are resolved by the browser using the current protocol, and are used to avoid making HTTP requests from an HTTPS page.
Code executing on the server doesn't really have a concept of a "current protocol". Whilst ASP.NET can determine whether the current request was issued over HTTP or HTTPS, the WebRequest classes are not restricted to ASP.NET applications, so they cannot rely on this.
You will need to specify the protocol. Whether you use HTTP or HTTPS will depend on whether you're concerned about third-parties eavesdropping on the connection between your server and "www.somedomain.com".
What about a two step process, check for the http version, if it doesn't exist check for https. I've quickly hacked together a basic example of how this could work but am not able to properly test and check it so it might need some tidying up/refactoring!
public virtual bool WebResourceExists(string url)
{
WebHeaderCollection headers = null;
WebResponse response = null;
try
{
if (url.StartsWith(#"//") {
url = "http:";
}
WebRequest request = WebRequest.Create(url);
request.Method = "HEAD";
response = request.GetResponse();
headers = response.Headers;
bool result = int.Parse(headers["Content-Length"]) > 0;
return result;
}
catch (System.Net.WebException)
{
if (url.StartsWith(#"http://") {
url = url.Replace("http://","https://");
} else {
return false;
}
try {
WebRequest request = WebRequest.Create(url);
request.Method = "HEAD";
response = request.GetResponse();
headers = response.Headers;
bool result = int.Parse(headers["Content-Length"]) > 0;
return result;
}
catch (System.Net.WebException)
{
return false;
}
}
catch (Exception e)
{
_log.Error(e);
return false;
}
finally
{
if (response != null)
{
response.Close();
}
}
}
In my project I'm using C# app client and tomcat6 web application server.
I wrote this snippet in the C# client:
public bool isServerOnline()
{
Boolean ret = false;
try
{
HttpWebRequest req = (HttpWebRequest)HttpWebRequest.Create(VPMacro.MacroUploader.SERVER_URL);
req.Method = "HEAD";
req.KeepAlive = false;
HttpWebResponse resp = (HttpWebResponse)req.GetResponse();
if (resp.StatusCode == HttpStatusCode.OK)
{
// HTTP = 200 - Internet connection available, server online
ret = true;
}
resp.Close();
return ret;
}
catch (WebException we)
{
// Exception - connection not available
Log.e("InternetUtils - isServerOnline - " + we.Status);
return false;
}
}
Everytime I invoke this method, I get a new session at server side.
I suppose it's because I should use HTTP cookies in my client. But I don't know how to do that, can you help me?
You must use a CookieContainer and keep the instance between calls.
private CookieContainer cookieContainer = new CookieContainer();
public bool isServerOnline()
{
Boolean ret = false;
try
{
HttpWebRequest req = (HttpWebRequest)HttpWebRequest.Create(VPMacro.MacroUploader.SERVER_URL);
req.CookieContainer = cookieContainer; // <= HERE
req.Method = "HEAD";
req.KeepAlive = false;
HttpWebResponse resp = (HttpWebResponse)req.GetResponse();
if (resp.StatusCode == HttpStatusCode.OK)
{
// HTTP = 200 - Internet connection available, server online
ret = true;
}
resp.Close();
return ret;
}
catch (WebException we)
{
// Exception - connection not available
Log.e("InternetUtils - isServerOnline - " + we.Status);
return false;
}
}
I'm trying to make a function that checks if a site is online or not, but is having some problem with the timeout. I want to limit it to a max 3 sec, if there is no respons within 3 sec I should see the page as offline.
My try:
class OnlineCheck
{
public static bool IsOnline(string url)
{
try
{
WebClient webclient = new WebClient();
webclient.Headers.Add(HttpRequestHeader.KeepAlive, "1000");
webclient.OpenRead(url);
}
catch { return false; }
return true;
}
}
The WebClient doesn't support timeout. But you can use the HttpWebRequest!
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(Endpoint);
request.Timeout=3000;
request.GetResponse();
If you want to check that the site is online, you are not really interested in the content of the page, just that you get a response. To make that more efficient, you should only request the http headers. Here is a quick example on how you could do:
private static IEnumerable<HttpStatusCode> onlineStatusCodes = new[]
{
HttpStatusCode.Accepted,
HttpStatusCode.Found,
HttpStatusCode.OK,
// add more codes as needed
};
private static bool IsSiteOnline(string url, int timeout)
{
HttpWebRequest request = WebRequest.Create(url) as HttpWebRequest;
{
if (request != null)
{
request.Method = "HEAD"; // get headers only
request.Timeout = timeout;
using (var response = request.GetResponse() as HttpWebResponse)
{
return response != null && onlineStatusCodes.Contains(response.StatusCode);
}
}
}
return false;
}
Use HttpWebRequest rather than WebClient. HttpWebRequest class has a timeout property.
You can try this code:
System.Net.WebRequest r = System.Net.WebRequest.Create("http://www.google.com");
r.Timeout = 3000;
System.Net.WebProxy proxy = new System.Net.WebProxy("<proxy address>");
System.Net.NetworkCredential credentials = new System.Net.NetworkCredential();
credentials.Domain = "<domain>";
credentials.UserName = "<login>";
credentials.Password = "<pass>";
proxy.Credentials = credentials;
r.Proxy = proxy;
try
{
System.Net.WebResponse rsp = r.GetResponse();
}
catch (Exception)
{
MessageBox.Show("Is not avaliable");
return;
}
MessageBox.Show("Avaliable!");
static bool isOnline (string URL)
{
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(URL);
request.Timeout = 3000;
try
{
WebResponse resp = request.GetResponse();
}
catch (WebException e)
{
if (((HttpWebResponse)e.Response).StatusCode == HttpStatusCode.NotFound)
{
return false;
}
}
return true;
}
I have a table in my database which contains the URLs of some websites. I have to open those URLs and verify some links on those pages. The problem is that some URLs get redirected to other URLs. My logic is failing for such URLs.
Is there some way through which I can pass my original URL string and get the redirected URL back?
Example: I am trying with this URL:
http://individual.troweprice.com/public/Retail/xStaticFiles/FormsAndLiterature/CollegeSavings/trp529Disclosure.pdf
It gets redirected to this one:
http://individual.troweprice.com/staticFiles/Retail/Shared/PDFs/trp529Disclosure.pdf
I tried to use following code:
HttpWebRequest req = (HttpWebRequest)WebRequest.Create(Uris);
req.Proxy = proxy;
req.Method = "HEAD";
req.AllowAutoRedirect = false;
HttpWebResponse myResp = (HttpWebResponse)req.GetResponse();
if (myResp.StatusCode == HttpStatusCode.Redirect)
{
MessageBox.Show("redirected to:" + myResp.GetResponseHeader("Location"));
}
When I execute the code above it gives me HttpStatusCodeOk. I am surprised why it is not considering it a redirection. If I open the link in Internet Explorer then it will redirect to another URL and open the PDF file.
Can someone help me understand why it is not working properly for the example URL?
By the way, I checked with Hotmail's URL (http://www.hotmail.com) and it correctly returns the redirected URL.
This function will return the final destination of a link — even if there are multiple redirects. It doesn't account for JavaScript-based redirects or META redirects. Notice that the previous solution didn't deal with Absolute & Relative URLs, since the LOCATION header could return something like "/newhome" you need to combine with the URL that served that response to identify the full URL destination.
public static string GetFinalRedirect(string url)
{
if(string.IsNullOrWhiteSpace(url))
return url;
int maxRedirCount = 8; // prevent infinite loops
string newUrl = url;
do
{
HttpWebRequest req = null;
HttpWebResponse resp = null;
try
{
req = (HttpWebRequest) HttpWebRequest.Create(url);
req.Method = "HEAD";
req.AllowAutoRedirect = false;
resp = (HttpWebResponse)req.GetResponse();
switch (resp.StatusCode)
{
case HttpStatusCode.OK:
return newUrl;
case HttpStatusCode.Redirect:
case HttpStatusCode.MovedPermanently:
case HttpStatusCode.RedirectKeepVerb:
case HttpStatusCode.RedirectMethod:
newUrl = resp.Headers["Location"];
if (newUrl == null)
return url;
if (newUrl.IndexOf("://", System.StringComparison.Ordinal) == -1)
{
// Doesn't have a URL Schema, meaning it's a relative or absolute URL
Uri u = new Uri(new Uri(url), newUrl);
newUrl = u.ToString();
}
break;
default:
return newUrl;
}
url = newUrl;
}
catch (WebException)
{
// Return the last known good URL
return newUrl;
}
catch (Exception ex)
{
return null;
}
finally
{
if (resp != null)
resp.Close();
}
} while (maxRedirCount-- > 0);
return newUrl;
}
The URL you mentioned uses a JavaScript redirect, which will only redirect a browser. So there's no easy way to detect the redirect.
For proper (HTTP Status Code and Location:) redirects, you might want to remove
req.AllowAutoRedirect = false;
and get the final URL using
myResp.ResponseUri
as there can be more than one redirect.
UPDATE: More clarification regarding redirects:
There's more than one way to redirect a browser to another URL.
The first way is to use a 3xx HTTP status code, and the Location: header. This is the way the gods intended HTTP redirects to work, and is also known as "the one true way." This method will work on all browsers and crawlers.
And then there are the devil's ways. These include meta refresh, the Refresh: header, and JavaScript. Although these methods work in most browsers, they are definitely not guaranteed to work, and occasionally result in strange behavior (aka. breaking the back button).
Most web crawlers, including the Googlebot, ignore these redirection methods, and so should you. If you absolutely have to detect all redirects, then you would have to parse the HTML for META tags, look for Refresh: headers in the response, and evaluate Javascript. Good luck with the last one.
Use this code to get redirecting URL
public void GrtUrl(string url)
{
HttpWebRequest webRequest = (HttpWebRequest)WebRequest.Create(url);
webRequest.AllowAutoRedirect = false; // IMPORTANT
webRequest.Timeout = 10000; // timeout 10s
webRequest.Method = "HEAD";
// Get the response ...
HttpWebResponse webResponse;
using (webResponse = (HttpWebResponse)webRequest.GetResponse())
{
// Now look to see if it's a redirect
if ((int)webResponse.StatusCode >= 300 &&
(int)webResponse.StatusCode <= 399)
{
string uriString = webResponse.Headers["Location"];
Console.WriteLine("Redirect to " + uriString ?? "NULL");
webResponse.Close(); // don't forget to close it - or bad things happen
}
}
}
Here's two Async HttpClient versions:
Works in .Net Framework and .Net Core
public static async Task<Uri> GetRedirectedUrlAsync(Uri uri, CancellationToken cancellationToken = default)
{
using var client = new HttpClient(new HttpClientHandler
{
AllowAutoRedirect = false,
}, true);
using var response = await client.GetAsync(uri, cancellationToken);
return new Uri(response.Headers.GetValues("Location").First();
}
Works in .Net Core
public static async Task<Uri> GetRedirectedUrlAsync(Uri uri, CancellationToken cancellationToken = default)
{
using var client = new HttpClient();
using var response = await client.GetAsync(uri, cancellationToken);
return response.RequestMessage.RequestUri;
}
P.S. handler.MaxAutomaticRedirections = 1 can be used if you need to limit the number of attempts.
After reviewing everyone's suggestions I kind of figured this out for at least my case which basically did 3 loops once to https and second one to actual ending location.
This is a recursive function call here:
public static string GrtUrl(string url, int counter)
{
ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls
| SecurityProtocolType.Tls11
| SecurityProtocolType.Tls12
| SecurityProtocolType.Ssl3;
string ReturnURL = url;
HttpWebRequest webRequest = (HttpWebRequest)WebRequest.Create(url);
webRequest.AllowAutoRedirect = false; // IMPORTANT
webRequest.Timeout = 10000; // timeout 10s
webRequest.Method = "HEAD";
// Get the response ...
HttpWebResponse webResponse;
using (webResponse = (HttpWebResponse)webRequest.GetResponse())
{
// Now look to see if it's a redirect
if ((int)webResponse.StatusCode >= 300 && (int)webResponse.StatusCode <= 399)
{
string uriString = webResponse.Headers["Location"];
ReturnURL = uriString;
if (ReturnURL == url)
{
webResponse.Close(); // don't forget to close it - or bad things happen!
return ReturnURL;
}
else
{
webResponse.Close(); // don't forget to close it - or bad things happen!
if (counter > 50)
return ReturnURL;
else
return GrtUrl(ReturnURL, counter++);
}
}
}
return ReturnURL;
}
You could check the Request.UrlReferrer.AbsoluteUri to see where i came from. If that doesn't work can you pass the old url as a query string parameter?
This code works for me
var request = (HttpWebRequest)HttpWebRequest.Create(url);
request.Method = "POST";
request.AllowAutoRedirect = true;
request.ContentType = "application/x-www-form-urlencoded";
var response = request.GetResponse();
//After sending the request and the request is expected to redirect to some page of your website, The response.ResponseUri.AbsoluteUri contains that url including the query strings
//(www.yourwebsite.com/returnulr?r=""... and so on)
Redirect(response.ResponseUri.AbsoluteUri); //then just do your own redirect.
Hope this helps
I had the same problem and after tryin a lot I couldn't get what i wanted with HttpWebRequest so i used web browser class to navigate to first url and then i could get the redirected url !
WebBrowser browser = new WebBrowser();
browser.Navigating += new System.Windows.Forms.WebBrowserNavigatingEventHandler(this.browser_Navigating);
string urlToNavigate = "your url";
browser.Navigate(new Uri(urlToNavigate));
then on navigating you can get your redirected url. Be careful that the first time browser_Navigating event handler occurs, e.url is the same url you used to start browsing so you can get redirected url on the second call
private void browser_Navigating(object sender, WebBrowserNavigatingEventArgs e)
{
Uri uri = e.Url;
}
This code worked for me with Unicode support:
public static string GetFinalRedirect(string url)
{
try
{
var request = (HttpWebRequest)HttpWebRequest.Create(url);
request.Method = "POST";
request.AllowAutoRedirect = true;
request.ContentType = "application/x-www-form-urlencoded";
var response = request.GetResponse();
return response.ResponseUri.AbsoluteUri.ToString();
}
catch(Exception ax)
{
return "";
}
}
string url = ".......";
var request = (HttpWebRequest)WebRequest.Create(url);
var response = (HttpWebResponse)request.GetResponse();
string redirectUrl = response.ResponseUri.ToString();
A way to deal with javascript redirect is to view the source code of the initial domain's page that would load and then extract a new domain aka the final domain directly from the source code. Since it is a javascript redirect then the new domain aka final domain should be there. Cheers
Code to extract the URL address from page source:
string href = "";
string pageSrc = "get page source using web client download string method and place output here";
Match m = Regex.Match(pageSrc, #"href=\""(.*?)\""", RegexOptions.Singleline);
if (m2.Success){
href = m.Groups[1].Value; /* will result in http://finalurl.com */
}
I made this method using your code and it returns the final redirected URL.
public string GetFinalRedirectedUrl(string url)
{
string result = string.Empty;
Uri Uris = new Uri(url);
HttpWebRequest req = (HttpWebRequest)WebRequest.Create(Uris);
//req3.Proxy = proxy;
req.Method = "HEAD";
req.AllowAutoRedirect = false;
HttpWebResponse myResp = (HttpWebResponse)req.GetResponse();
if (myResp.StatusCode == HttpStatusCode.Redirect)
{
string temp = myResp.GetResponseHeader("Location");
//Recursive call
result = GetFinalRedirectedUrl(temp);
}
else
{
result = url;
}
return result;
}
Note: myResp.ResponseUri does not return the final URL