Client HTTP Stack: HttpWebRequest and non-ASCII characters in HTTP response headers

Client HTTP Stack in Silverlight seems to bee too strict sometimes. I have an OOB application that uses HttpWebRequest object to get data from external web service.

Unfortunately, HTTP response from the service includes header that contains non-ASCII characters. And it turns out to be a problem. See code snippet below:

void GetResponseCallback(IAsyncResult ar) {
    HttpWebRequest request = (HttpWebRequest)ar.AsyncState;
    WebResponse response = request.EndGetResponse(ar);
    // code continues …
}

EndGetResponse() call results in System.ArgumentException: Specified value has invalid Control characters. Parameter name: value.

I’m not sure whether it is a bug or designed behaviour. But it’s a pity that invalid header prevents application from obtaining response at all. In fact I don’t even need that header, so my workaround was to switch to browser http handling so that I can move on.

And just for the record: the same code works fine in WPF application.

Silverlight OOB applications and HTTP handling

With Silverlight, you can specify whether the browser or the client provides HTTP handling for your Silverlight-based applications. By default, HTTP handling is performed by the browser and you must opt-in to client HTTP handling.

Surprisingly, despite of what your intuition might suggest, Silverlight out of browser applications use browser HTTP handling by default. At least for WCF service calls :)