I need to check if the url content type is pdf or not? I have a working code however i was wondering what's the best way to check from what i have. I don't need to display the pdf, just need to check if the content type is pdf or not?
Note: This method will be called multiple times with different url, so i am not sure if i need to close the response or not.
here is my code.
private bool IsValid(string url)
{
bool isValid = false;
var request = (HttpWebRequest)WebRequest.Create(url);
var response = (HttpWebResponse)request.GetResponse();
if(response.StatusCode == HttpStatusCode.OK && response.ContentType == "application/pdf")
{
isValid = true;
}
response.Close();
return isValid;
}
Yes as you don't pass response anywhere you need to dispose it. You should also catch WebException and dispose stream from there too (also I would expect disposing response or even request would close all related resource, but unfortunately I never seen documentation that confirms such cascading dispose behavior for Response object).
You also need to close/dispose the request as it is one-use object. It is specified in note of GetResponse:
Multiple calls to GetResponse return the same response object; the request is not reissued.
Side note: Consider making HEAD request so you don't get any stream at all (see Method property for usage).
var request = (HttpWebRequest)WebRequest.Create(url);
request.Method = "HEAD";
When logging the login process using Firebug i see that it is like this
POST //The normal post request
GET //Automatically made after the login
GET //Automatically made after the login
GET //Automatically made after the login
When making a post request using my code below it did not make the automatic GET requests that the browsers is doing.
MY WebClient Handler
using System;
using System.Net;
namespace Test
{
class HttpHandler : WebClient
{
private CookieContainer _mContainer = new CookieContainer();
protected override WebRequest GetWebRequest(Uri address)
{
var request = base.GetWebRequest(address);
if (request is HttpWebRequest)
{
(request as HttpWebRequest).CookieContainer = _mContainer;
}
return request;
}
protected override WebResponse GetWebResponse(WebRequest request)
{
var response = base.GetWebResponse(request);
if (response is HttpWebResponse)
_mContainer.Add((response as HttpWebResponse).Cookies);
return response;
}
public void ClearCookies()
{
_mContainer = new CookieContainer();
}
}
}
Using Code
private static async Task<byte[]> LoginAsync(string username, string password)
{
var postData = new NameValueCollection();
var uri = new Uri(string.Format("http://{0}/", ServerName));
postData.Add("name", username);
postData.Add("password", password);
return await HttpHandler.UploadValuesTaskAsync(uri, postData);
}
When trying to track the connection of my application it is only doing the POST Request and not the rest of GET requests. [THAT ARE MADE AUTOMATICALLY IN THE BROWSER]
Try adding
request.AllowAutoRedirect = true;
right under the
var request = base.GetWebRequest(address);
It solved some similar problems for me, even though AllowAutoRedirect is supposed to be true by default.
That shouldn't be surprising, given that HttpWebRequest is not a browser. If you need to perform these redirects, then check the HttpWebResponse.StatusCode, and make another request if it's a redirect code in the 300's. Note from the link under 10.3 Redirection 3xx:
This class of status code indicates that further action needs to be taken by the user agent in order to fulfill the request. The action required MAY be carried out by the user agent without interaction with the user if and only if the method used in the second request is GET or HEAD. A client SHOULD detect infinite redirection loops, since such loops generate network traffic for each redirection.
I'm currently writing a simple app that performs a series of requests to the web server and I've encountered a strange... feature?
I don't need response stream of the request, but only status code. So, for each piece of my data I call my own "Send" method:
public static int Send(string uri)
{
HttpWebRequest request = null;
HttpWebResponse response = null;
try
{
request = (HttpWebRequest)WebRequest.Create(uri);
response = (HttpWebResponse)request.GetResponse();
if (response.StatusCode == HttpStatusCode.OK) return 0;
}
catch (Exception e)
{
if (request != null) request.Abort();
}
return -1;
}
Works fine? Yes, unless I call this function at least twice. Second call of such a function in a row (with the same uri) will ALWAYS result in timeout.
Now, that's odd: if I add request.Abort(); when I return zero (here, when status code is 200) - everything ALWAYS works fine.
So my question is - why? Is it some kind of framework restriction, or maybe the some kind of anti-DOS protection on the particular server (unfortunately, the server is a black box for me)? Or maybe I just don't understand smth in how it all works?
Try to dispose of the web response, you may leak some resources
public static int Send(string uri)
{
HttpWebRequest request = null;
try
{
request = (HttpWebRequest)WebRequest.Create(uri);
using (var response = (HttpWebResponse)request.GetResponse())
{
if (response.StatusCode == HttpStatusCode.OK) return 0;
}
}
catch (Exception e)
{
if (request != null) request.Abort();
}
return -1;
}
There is also a default number of connections (2 I think, but you can configure this) you can make to a domain simultaneously, please see this SO question. You're probably hitting this limit with your unclosed responses.
First of all I'd make a series of changes in order to get to the root of this:
take out that try..catch{} (you're likely swallowing an exception)
return a boolean instead of a number
You should then get your exception information you need.
Also you should be using "HEAD" as your method as you only want the status code:
request.Method = "HEAD";
read the difference here.
How can I read the HTTP response headers from a web service response in C#?
After digging through MSDN, all I needed to do was to override the GetWebResponse method, and then I could access the response headers:
public class MyWSProxy : HttpWebClientProtocol
{
protected override WebResponse GetWebResponse(WebRequest request)
{
System.Net.WebResponse wr = base.GetWebResponse(request);
// read a response header
object val = wr.Headers["key"];
return wr;
}
}
If you're getting back an HttpResponse, you can just query the HttpResponse.Headers property.
Can't you just refer to HttpContext.Current.Response.Headers in your webservice?
I'm not sure if that'll work.
I am making a simple program in visual c# 2005 that looks up a stock symbol on Yahoo! Finance, downloads the historical data, and then plots the price history for the specified ticker symbol.
I know the exact URL that I need to acquire the data, and if the user inputs an existing ticker symbol (or at least one with data on Yahoo! Finance) it works perfectly fine. However, I have a run-time error if the user makes up a ticker symbol, as the program tries to pull data from a non-existent web page.
I am using the WebClient class, and using the DownloadString function. I looked through all the other member functions of the WebClient class, but didn't see anything I could use to test a URL.
How can I do this?
Here is another implementation of this solution:
using System.Net;
///
/// Checks the file exists or not.
///
/// The URL of the remote file.
/// True : If the file exits, False if file not exists
private bool RemoteFileExists(string url)
{
try
{
//Creating the HttpWebRequest
HttpWebRequest request = WebRequest.Create(url) as HttpWebRequest;
//Setting the Request method HEAD, you can also use GET too.
request.Method = "HEAD";
//Getting the Web Response.
HttpWebResponse response = request.GetResponse() as HttpWebResponse;
//Returns TRUE if the Status code == 200
response.Close();
return (response.StatusCode == HttpStatusCode.OK);
}
catch
{
//Any exception will returns false.
return false;
}
}
From: http://www.dotnetthoughts.net/2009/10/14/how-to-check-remote-file-exists-using-c/
You could issue a "HEAD" request rather than a "GET"?
So to test a URL without the cost of downloading the content:
// using MyClient from linked post
using(var client = new MyClient()) {
client.HeadOnly = true;
// fine, no content downloaded
string s1 = client.DownloadString("http://google.com");
// throws 404
string s2 = client.DownloadString("http://google.com/silly");
}
You would try/catch around the DownloadString to check for errors; no error? It exists...
With C# 2.0 (VS2005):
private bool headOnly;
public bool HeadOnly {
get {return headOnly;}
set {headOnly = value;}
}
and
using(WebClient client = new MyClient())
{
// code as before
}
These solutions are pretty good, but they are forgetting that there may be other status codes than 200 OK. This is a solution that I've used on production environments for status monitoring and such.
If there is a url redirect or some other condition on the target page, the return will be true using this method. Also, GetResponse() will throw an exception and hence you will not get a StatusCode for it. You need to trap the exception and check for a ProtocolError.
Any 400 or 500 status code will return false. All others return true.
This code is easily modified to suit your needs for specific status codes.
/// <summary>
/// This method will check a url to see that it does not return server or protocol errors
/// </summary>
/// <param name="url">The path to check</param>
/// <returns></returns>
public bool UrlIsValid(string url)
{
try
{
HttpWebRequest request = HttpWebRequest.Create(url) as HttpWebRequest;
request.Timeout = 5000; //set the timeout to 5 seconds to keep the user from waiting too long for the page to load
request.Method = "HEAD"; //Get only the header information -- no need to download any content
using (HttpWebResponse response = request.GetResponse() as HttpWebResponse)
{
int statusCode = (int)response.StatusCode;
if (statusCode >= 100 && statusCode < 400) //Good requests
{
return true;
}
else if (statusCode >= 500 && statusCode <= 510) //Server Errors
{
//log.Warn(String.Format("The remote server has thrown an internal error. Url is not valid: {0}", url));
Debug.WriteLine(String.Format("The remote server has thrown an internal error. Url is not valid: {0}", url));
return false;
}
}
}
catch (WebException ex)
{
if (ex.Status == WebExceptionStatus.ProtocolError) //400 errors
{
return false;
}
else
{
log.Warn(String.Format("Unhandled status [{0}] returned for url: {1}", ex.Status, url), ex);
}
}
catch (Exception ex)
{
log.Error(String.Format("Could not test url {0}.", url), ex);
}
return false;
}
If I understand your question correctly, you could use a small method like this to give you the results of your URL test:
WebRequest webRequest = WebRequest.Create(url);
WebResponse webResponse;
try
{
webResponse = webRequest.GetResponse();
}
catch //If exception thrown then couldn't get response from address
{
return 0;
}
return 1;
You could wrap the above code in a method and use it to perform validation. I hope this answers the question you were asking.
Try this (Make sure you use System.Net):
public bool checkWebsite(string URL) {
try {
WebClient wc = new WebClient();
string HTMLSource = wc.DownloadString(URL);
return true;
}
catch (Exception) {
return false;
}
}
When the checkWebsite() function gets called, it tries to get the source code of
the URL passed into it. If it gets the source code, it returns true. If not,
it returns false.
Code Example:
//The checkWebsite command will return true:
bool websiteExists = this.checkWebsite("https://www.google.com");
//The checkWebsite command will return false:
bool websiteExists = this.checkWebsite("https://www.thisisnotarealwebsite.com/fakepage.html");
I have always found Exceptions are much slower to be handled.
Perhaps a less intensive way would yeild a better, faster, result?
public bool IsValidUri(Uri uri)
{
using (HttpClient Client = new HttpClient())
{
HttpResponseMessage result = Client.GetAsync(uri).Result;
HttpStatusCode StatusCode = result.StatusCode;
switch (StatusCode)
{
case HttpStatusCode.Accepted:
return true;
case HttpStatusCode.OK:
return true;
default:
return false;
}
}
}
Then just use:
IsValidUri(new Uri("http://www.google.com/censorship_algorithm"));
A lot of the answers are older than HttpClient (I think it was introduced in Visual Studio 2013) or without async/await functionality, so I decided to post my own solution:
private static async Task<bool> DoesUrlExists(String url)
{
try
{
using (HttpClient client = new HttpClient())
{
//Do only Head request to avoid download full file
var response = await client.SendAsync(new HttpRequestMessage(HttpMethod.Head, url));
if (response.IsSuccessStatusCode) {
//Url is available is we have a SuccessStatusCode
return true;
}
return false;
}
} catch {
return false;
}
}
I use HttpClient.SendAsync with HttpMethod.Head to make only a head request, and not downlaod the whole file. Like David and Marc already say there is not only http 200 for ok, so I use IsSuccessStatusCode to allow all Sucess Status codes.
WebRequest request = WebRequest.Create("http://www.google.com");
try
{
request.GetResponse();
}
catch //If exception thrown then couldn't get response from address
{
MessageBox.Show("The URL is incorrect");`
}
This solution seems easy to follow:
public static bool isValidURL(string url) {
WebRequest webRequest = WebRequest.Create(url);
WebResponse webResponse;
try
{
webResponse = webRequest.GetResponse();
}
catch //If exception thrown then couldn't get response from address
{
return false ;
}
return true ;
}
Here is another option
public static bool UrlIsValid(string url)
{
bool br = false;
try {
IPHostEntry ipHost = Dns.Resolve(url);
br = true;
}
catch (SocketException se) {
br = false;
}
return br;
}
A lot of other answers are using WebRequest which is now obsolete.
Here is a method that has minimal code and uses currently up-to-date classes and methods.
I have also tested the other most up-voted functions which can produce false positives.
I tested with these URLs, which points to the Visual Studio Community Installer, found on this page.
//Valid URL
https://aka.ms/vs/17/release/vs_community.exe
//Invalid URL, redirects. Produces false positive on other methods.
https://aka.ms/vs/14/release/vs_community.exe
using System.Net;
using System.Net.Http;
//HttpClient is not meant to be created and disposed frequently.
//Declare it staticly in the class to be reused.
static HttpClient client = new HttpClient();
/// <summary>
/// Checks if a remote file at the <paramref name="url"/> exists, and if access is not restricted.
/// </summary>
/// <param name="url">URL to a remote file.</param>
/// <returns>True if the file at the <paramref name="url"/> is able to be downloaded, false if the file does not exist, or if the file is restricted.</returns>
public static bool IsRemoteFileAvailable(string url)
{
//Checking if URI is well formed is optional
Uri uri = new Uri(url);
if (!uri.IsWellFormedOriginalString())
return false;
try
{
using (HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Head, uri))
using (HttpResponseMessage response = client.Send(request))
{
return response.IsSuccessStatusCode && response.Content.Headers.ContentLength > 0;
}
}
catch
{
return false;
}
}
Just note that this will not work with .NET Framework, as HttpClient.Send does not exist.
To get it working on .NET Framework you will need to change client.Send(request) to client.SendAsync(request).Result.
Web servers respond with a HTTP status code indicating the outcome of the request e.g. 200 (sometimes 202) means success, 404 - not found etc (see here). Assuming the server address part of the URL is correct and you are not getting a socket timeout, the exception is most likely telling you the HTTP status code was other than 200. I would suggest checking the class of the exception and seeing if the exception carries the HTTP status code.
IIRC - The call in question throws a WebException or a descendant. Check the class name to see which one and wrap the call in a try block to trap the condition.
i have a more simple way to determine weather a url is valid.
if (Uri.IsWellFormedUriString(uriString, UriKind.RelativeOrAbsolute))
{
//...
}
Following on from the examples already given, I'd say, it's best practice to also wrap the response in a using like this
public bool IsValidUrl(string url)
{
try
{
var request = WebRequest.Create(url);
request.Timeout = 5000;
request.Method = "HEAD";
using (var response = (HttpWebResponse)request.GetResponse())
{
response.Close();
return response.StatusCode == HttpStatusCode.OK;
}
}
catch (Exception exception)
{
return false;
}
}