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c# - Windows Phone - failing to get a string from a website with login information

问题描述:

I am new to accessing web services with Windows Phone 7/8. I'm using a WebClient to get a string from a php-website. The site returns a JSON string but at the moment I'm just trying to put it into a TextBox as a normal string just to test if the connection works.

The php-page requires an authentication and I think that's where my code is failing. Here's my code:

WebClient client = new WebClient();

client.Credentials = new NetworkCredential("myUsername", "myPassword");

client.DownloadStringCompleted += new DownloadStringCompletedEventHandler(client_DownloadStringCompleted);

client.DownloadStringAsync(new Uri("https://www.mywebsite.com/ba/php/jsonstuff.php"));

void client_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)

{

try

{

string data = e.Result;

this.jsonText.Text = data;

}

catch (Exception ex)

{

System.Diagnostics.Debug.WriteLine(ex.Message);

}

}

This returns first a WebException and then a TargetInvocationException. If I replace the Uri with for example "http://www.google.com/index.html" the jsonText TextBox gets filled with html text from Google (oddly enough, this also works even when the WebClient credentials are still set).

So is the problem in the setting of the credentials? I couldn't find any good results when searching for guides on how to access php-pages with credentials, only without them. Then I found a short mention somewhere to use the WebClient.Credentials property. But should it work some other way?

Update: here's what I can get out of the WebException (sorry for the bad formatting):

System.Net.WebException: The remote server returned an error: NotFound. --->System.Net.WebException: The remote server returned an error: NotFound.

at System.Net.Browser.ClientHttpWebRequest.InternalEndGetResponse(IAsyncResult asyncResult)

at System.Net.Browser.ClientHttpWebRequest.<>c_DisplayClasse.b_d(Object sendState)

at System.Net.Browser.AsyncHelper.<>c_DisplayClass1.b_0(Object sendState)

--- End of inner exception stack trace ---

at System.Net.Browser.AsyncHelper.BeginOnUI(SendOrPostCallback beginMethod, Object state)

at System.Net.Browser.ClientHttpWebRequest.EndGetResponse(IAsyncResult asyncResult)

at System.Net.WebClient.GetWebResponse(WebRequest request, IAsyncResult result)

at System.Net.WebClient.DownloadBitsResponseCallback(IAsyncResult result)

Update 2: Here's the error log line:

Nov 16 17:51:12 myservice httpd[21036]: 127.0.0.1 - - [16/Nov/2012:17:51:12 +0200] "GET /ba/php/jsonstuff.php?origpath=/ba/php/jsonstuff.php HTTP/1.1" 401 290 "-" "Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.2; WOW64; Trident/6.0)"

401 I guess would suggest false credentials?

网友答案:

In my opininion you really need to see how the server handles your request. "NotFound" in WebException could mean that you're referring to a location that doesn't exist. But I'm sure that you pass the right URL. So there must be some logic on the server that redirects you. If you go to the url using your desktop browser - do you have any kind of SSL certificate error or warning? Maybe that's the reason. Try navigating on your phone using IE. Or you could set up another host just to give it a try.

I'll set up a host on my machine and try it.

The problem is with the SSL certificate I guess. WP is very strict when it goes to checking SSL certificates, so you should try without ssl or install cert on your emulator/phone or install valid (not self generated) cert on your server.

网友答案:

Okay, so I found a way to get this working. The problem was that the WebClient class couldn't properly handle the cookies of the web service.

After some Google searches I found this solution and it works perfectly: http://firebelly.net/post/3341374382/cookie-aware-webclient-for-wp7

So basically you just make your own client class that extends the WebClient class which can store cookies.

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