21 Nov 2012

Just a quick post about decompressing web requests in .Net. Beat The Bookie makes calls to the William Hill API for market prices, but when making a call to it using DownloadString from the WebClient type, returned random characters. I spun up fiddler and saw that the response was being compressed.

Here is my solution for solving this:

public class WebClientWithCompression : WebClient 
{ 
    protected override WebRequest GetWebRequest(Uri address) 
    { 
        var request = base.GetWebRequest(address) as HttpWebRequest; 
        request.AutomaticDecompression = DecompressionMethods.Deflate | DecompressionMethods.GZip; 
        return request; 
    } 
}

I created a WebClientWithCompression class that inherits from WebClient (I still want to use some of the inheritedÿbehavior; I then overrode the GetWebRequest method. I still make a call to the base GetWebRequest (as there is no need to rewrite this functionality) but this allows me to intercept the request and set the automatic decompression mode.

I can now instantiate the WebClientWithCompression class and invoke all the defaultÿbehaviorÿthat exists in WebClient; having overridden the GetWebRequest method, the DownloadString method on the WebClient returns the string as expected. Voila! quite simple

using (var client = new WebClientWithCompression()) 
    html = client.DownloadString(url);

Let me know what you think? I am doing this incorrectly? Is there a better way? I’d like to hear from anyone.