C＃-WP8.1应用程序中的Web用户代理

Question

One question that's been confusing me and could really do with some insight.

I need to retreive Json objects from a http service. When I tested this in a Console Window, I kept receiving a "Internal Server Error : 500" until I set the UserAgent property for the WebClient object. Example:

WebClient client = new WebClient();
client.Headers.Add("user-agent", "Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/40.0.2214.94 Safari/537.36");
content = client.DownloadString(url);

Now, if I need to do the same for a WP8.1 app, how would I detect (if I need to in the first place?) the UserAgent (and set it) and be able to retrieve the data?

Thank you all.

Answer 1

Windows Phone 8.1 App will use HttpClient. By default there will not be a user agent set. The default user-agent for the phones web browser is:

"Mozilla/5.0 (Mobile; Windows Phone 8.1; Android 4.0; ARM; Trident/7.0; Touch; rv:11.0; IEMobile/11.0; NOKIA; Lumia 520) like iPhone OS 7_0_3 Mac OS X AppleWebKit/537 (KHTML, like Gecko) Mobile Safari/537"

You can manually set the user-agent on the HttpRequestMessage.Headers.UserAgent property.

References:

HttpClient

https://msdn.microsoft.com/en-us/library/windows/apps/xaml/windows.web.http.headers.httprequestheadercollection.aspx

User-Agent

https://msdn.microsoft.com/en-us/library/ie/hh869301(v=vs.85).aspx#ie11 \\

Answer 2

The class libraries for using http do not add any User Agents by default. See these lines from the msdn page:

By default, no user-agent header is sent with the HTTP request to the web service by the HttpClient object. Some HTTP servers, including some Microsoft web servers, require that a user-agent header be included with the HTTP request sent from the client. The user-agent header is used by the HTTP server to determine how to format some HTTP pages so they render better on the client for different web browsers and form factors (mobile phones, for example). Some HTTP servers return an error if no user-agent header is present on the client request. We need to add a user-agent header to avoid these errors using classes in the Windows.Web.Http.Headers namespace. We add this header to the HttpClient.DefaultRequestHeaders property.

For more details, refer the link below:

How to connect to an HTTP server using Windows.Web.Http.HttpClient (XAML)

Also look at the answer below (by Bret Bentzinger) for the exact user agent string.