[IronPython] Silverlight and Catching HttpWebRequest Errors

[Jimmy Schementi]

So, did some homework on this. Taking a look at BrowserHttpWebRequest with Reflector, it definitely has a public ProgressFailed event, but it says it's read-only.

Dino/Curt, could this behavior happen because BrowserHttpWebRequest has a methods and events by exactly the same name?

    private EventHandler<NetworkProgressChangedEventArgs> ProgressChanged;
    private EventHandler<NetworkProgressChangedEventArgs> ProgressCompleted;
    private EventHandler<NetworkProgressChangedEventArgs> ProgressFailed;

    // Events
    public event EventHandler<NetworkProgressChangedEventArgs> ProgressChanged;
    public event EventHandler<NetworkProgressChangedEventArgs> ProgressCompleted;
    public event EventHandler<NetworkProgressChangedEventArgs> ProgressFailed;

Michael, regardless, for simple downloading I'd use WebClient; the code is much more concise:

from System.Net import WebClient
from System import Uri

def Downloaded(sender, args):
    print args.Result

uri = Uri('http://localhost:2060/index.html')
req = WebClient()
req.DownloadStringCompleted += Downloaded
req.DownloadStringAsync(uri)

Do you still have time to change your book's example? =P

~Jimmy

> -----Original Message-----
> From: users-bounces at lists.ironpython.com [mailto:users-
> bounces at lists.ironpython.com] On Behalf Of Michael Foord
> Sent: Wednesday, May 14, 2008 2:58 PM
> To: Discussion of IronPython
> Subject: Re: [IronPython] Silverlight and Catching HttpWebRequest
> Errors
>
> Michael Foord wrote:
> > Michael Foord wrote:
> >> On May 12, 9:17 am, Jimmy Schementi <Jimmy.Scheme... at microsoft.com>
> >> wrote:
> >>
> >>> The actual type returned by HttpWebRequest.Create() is a
> >>> BrowserHttpWebRequest, but it's internal (not sure why). Anyway, it
> >>> has a ProgressFailed event you can hook.
> >>>
> >>
> >> Hello Jimmy,
> >>
> >> As far as I can tell it *doesn't* have the 'ProgressFailed' event.
> >>
> >
> > The actual failure I see is:
> >
> > Exception: [Arg_COMException]
> > Arguments:
> > Debugging resource strings are unavailable. Often the key and
> > arguments provide sufficient information to diagnose the problem. See
> >
> http://go.microsoft.com/fwlink/?linkid=106663&Version=2.0.30226.1&File=
> mscorlib.dll&Key=Arg_COMException
> >
> >
> >
>
> Sorry for the noise. This one is actually for the sake of google (and
> all who sail in her).
>
> Exception
>    at MS.Internal.XcpImports.GetDownloaderBytes(IntPtr element, IntPtr&
> outBytes, Int32& outSize)
>    at MS.Internal.InternalWebRequest.GetResponseStream()
>    at System.Net.BrowserHttpWebRequest.Completed(Object sender,
> EventArgs e)
>    at System.Windows.CoreInvokeHandler.InvokeEventHandler(Int32
> typeIndex, Delegate handlerDelegate, Object sender, Object args)
>    at MS.Internal.JoltHelper.FireEvent(IntPtr unmanagedObj, IntPtr
> unmanagedObjArgs, Int32 argsTypeIndex, String eventName)
>
> Michael
>
> > This is using Safari. As I'm developing on the Mac I can't use
> > debugging, nor can I test in Firefox because of the bug in Chiron.
> >
> > It looks like some people have similar errors:
> >
> >    http://silverlight.net/forums/p/12500/40967.aspx#40967
> >
> > and a guy in the comments here:
> >
> >
> > http://www.cameronalbert.com/post/2008/03/HttpWebRequest-Helper-for-
> Silverlight-2.aspx
> >
> >
> > All the best,
> >
> > Michael Foord
> > http://www.ironpythoninaction.com/
> >
> >> I need to make cross-domain POST, and although the request gets made
> >> successfully I'm getting a COM Arg Exception everytime (I think
> >> because the server is slow to respond). This is screwing me at the
> >> moment.
> >>
> >> FYI - when I execute the following code in Silverlight:
> >>
> >>   from System.Net import WebRequest
> >>   from System import Uri
> >>
> >>   u = Uri('http://www.v.com')
> >>   req = WebRequest.Create(u)
> >>   print req.ProgressFailed
> >>
> >> I get the following exception:
> >>
> >> Traceback (most recent call last):
> >>   File "None", line 6, in <undefined>
> >> AttributeError: 'BrowserHttpWebRequest' object has no attribute
> >> 'ProgressFailed'
> >>
> >> All the best,
> >>
> >> Michael Foord
> >> http://www.ironpythoninaction.com/
> >>
> >>
> >>> PS. If you REALLY want synchronous downloading, just hack on
> >>> XMLHttpRequest
> >>>
> >>> def download(url):
> >>>     request = HtmlPage.Window.CreateInstance("XMLHttpRequest")
> >>>     request.Invoke("open", "GET", url, false) # false means
> synchronous
> >>>     request.Invoke("send", "")
> >>>     return request.GetProperty("responseText")
> >>>
> >>> :)
> >>>
> >>> ~js
> >>> ________________________________________
> >>> From: users-boun... at lists.ironpython.com
> >>> [users-boun... at lists.ironpython.com] On Behalf Of Michael Foord
> >>> [fuzzy... at voidspace.org.uk]
> >>> Sent: Monday, May 12, 2008 12:58 AM
> >>> To: Discussion of IronPython
> >>> Subject: [IronPython] Silverlight and Catching HttpWebRequest
> Errors
> >>>
> >>> Hello guys,
> >>>
> >>> I have a problem with catching network errors raised by
> HttpWebRequest
> >>> in Silverlight. (Not necessarily an IronPython specific question -
> but
> >>> you guys are so intelligent you are always the first place I
> turn...)
> >>>
> >>> HttpWebRequest uses an async model for fetching resources. If there
> >>> is a
> >>> problem (triggered usually by a slow response from the server),
> then it
> >>> can happen *after* I have made the request - but before my callback
> is
> >>> invoked. This gives me nowhere to catch the exception, as
> >>> effectively it
> >>> happens 'inside Silverlight'. I wondered if there was a solution...
> ?
> >>>
> >>> def callback(asyncResult):
> >>>     ...
> >>>
> >>> uri = Uri(some_url)
> >>> req = HttpWebRequest.Create(uri)
> >>>
> >>> req.BeginGetResponse(AsyncCallback(callback), object())
> >>>
> >>> The error occurs after BeginGetResponse, but before calback. Any
> ideas
> >>> for catching it?
> >>>
> >>> Michael Foordhttp://www.ironpythoninaction.com/
> >>>
> >>> _______________________________________________
> >>> Users mailing list
> >>>
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> s-ironpython.com
> >>>
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> >>>
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