c# - The remote server returned an error: (403) Forbidden

Question

I've written an app that has worked fine for months, in the last few days I've been getting the error below on the installed version only.

If I run the source code in VS everything works fine. Also, the .exe in the bin folders work fine. It's only the installed version which generates the error, if I recompile and reinstall I get the same error.

I'm a bit stumped as to what's causing this and hoped for a few pointers. It seems to be a WebRequest response through IE is not being returned but I'm stumped as to why it works fine in VS without any errors. Are there any new IE security measures/polices that may cause this?

Things I've tried so far include:

• Disabled all AntiVirus & Firewall
• Run as Administrator

The Exception:

Exception: System.Windows.Markup.XamlParseException: The invocation of the constructor on type 'XApp.MainWindow' that matches the specified binding constraints threw an exception. ---> System.Net.WebException: The remote server returned an error: (403) Forbidden.
   at System.Net.HttpWebRequest.GetResponse()
   at XApp.HtmlRequest.getHtml(Uri uri) in J:PathMainWindow.xaml.cs:line 3759
   at XApp.MainWindow.GetLinks() in J:PathMainWindow.xaml.cs:line 2454
   at XApp.MainWindow..ctor() in J:PathMainWindow.xaml.cs:line 124
   --- End of inner exception stack trace ---
   at System.Windows.Markup.WpfXamlLoader.Load(XamlReader xamlReader, IXamlObjectWriterFactory writerFactory, Boolean skipJournaledProperties, Object rootObject, XamlObjectWriterSettings settings, Uri baseUri)
   at System.Windows.Markup.WpfXamlLoader.LoadBaml(XamlReader xamlReader, Boolean skipJournaledProperties, Object rootObject, XamlAccessLevel accessLevel, Uri baseUri)
   at System.Windows.Markup.XamlReader.LoadBaml(Stream stream, ParserContext parserContext, Object parent, Boolean closeStream)
   at System.Windows.Application.LoadBamlStreamWithSyncInfo(Stream stream, ParserContext pc)
   at System.Windows.Application.LoadComponent(Uri resourceLocator, Boolean bSkipJournaledProperties)
   at System.Windows.Application.DoStartup()
   at System.Windows.Application.<.ctor>b__1(Object unused)
   at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
   at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler)
Exception: System.Net.WebException: The remote server returned an error: (403) Forbidden.
   at System.Net.HttpWebRequest.GetResponse()
   at XApp.HtmlRequest.getHtml(Uri uri) in J:PathMainWindow.xaml.cs:line 3759
   at XApp.MainWindow.GetLinks() in J:PathMainWindow.xaml.cs:line 2454
   at XApp.MainWindow..ctor() in J:PathMainWindow.xaml.cs:line 124

EDIT:

This is installed as a standalone app. When I've run as Administrator, I've opened the program folder and run the exe as administrator rather than the shortcut.

The code that causes the issue is this

private void GetLinks()
{
    //Navigate to front page to Set cookies
    HtmlRequest htmlReq = new HtmlRequest();

    OLinks = new Dictionary<string, List<string>>();

    string Url = "http://www.somesite.com/somepage";
    CookieContainer cookieJar = new CookieContainer();
    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(Url);
    request.CookieContainer = cookieJar;

    request.Accept = @"text/html, application/xhtml+xml, */*";
    request.Referer = @"http://www.somesite.com/";
    request.Headers.Add("Accept-Language", "en-GB");
    request.UserAgent = @"Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.2; Trident/6.0)";
    request.Host = @"www.somesite.com";

    HttpWebResponse response = (HttpWebResponse)request.GetResponse();
    String htmlString;
    using (var reader = new StreamReader(response.GetResponseStream()))
    {
        htmlString = reader.ReadToEnd();
    }

    //More Code


 }

Answer 1

Add the following line:

request.UseDefaultCredentials = true;

This will let the application use the credentials of the logged in user to access the site. If it's returning 403, clearly it's expecting authentication.

It's also possible that you (now?) have an authenticating proxy in between you and the remote site. In which case, try:

request.Proxy.Credentials = System.Net.CredentialCache.DefaultCredentials;

Hope this helps.