C# HttpWebRequest - Using Gzip Compression

Question

I have a program which makes lots of HttpWebRequests, and I read about using gzip compression to speed up the downloading of the response data. I know what gzip is, and how it works, but I don't know how it works in C#.

Let's say I have a simple GET request:

HttpWebRequest request = (HttpWebRequest)WebRequest.Create("http://google.com");
request.Method = "GET";
WebResponse response = request.GetResponse();

How could I make the response data be compressed in gzip? How can I show the compressed size, and then the un-compressed size?

Thanks

score 9 · Answer 1 · edited May 23 '17 at 10:29

9

See this page for a synopsis of how GZip works with web requests in general.

The specific header you're going to need to send is Accept-Encoding: gzip. Normally, you'd need to add this to the request yourself (via the Headers collection), but there's a shortcut. Per this answer, all you need to do is add

request.AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate;

to your code.

Note that you probably won't be able to get the compressed/uncompressed sizes doing this - the request will automatically decompress it as it comes in. However, since you can't know ahead of time whether the server will even try to send you GZipped pages, it's not a useful thing to be testing.

edited May 23 '17 at 10:29

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answered Sep 25 '13 at 14:05

Bobson

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After, if I want to read the data from the response, which I would normally just use a StreamReader for, do I need to do anything special? – user2764359 Sep 25 '13 at 14:07
Nope. That's why it's *Automatic* Decompression. It'll handle it all for you, as far as I can tell. (I haven't tried this myself, but I will, now that I know about it!) – Bobson Sep 25 '13 at 14:10

score 3 · Accepted Answer · answered Sep 25 '13 at 14:06

Make sure you state in your request that you can accept gzip'd responses. So, after your code to create the request, do this:

request.Headers.Add("Accept-Encoding", "gzip");

This will tell the server to return it zipped, if it can.

The only way I can think to show the size difference would be t make 2 calls, one with compression and one not, and compare the length of the returned response streams.

C# HttpWebRequest - Using Gzip Compression

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