How do I get a WCF
client to process server responses which have been GZipped or Deflated by IIS?
On IIS, I've followed
the instructions here on how to make IIS 6 gzip all responses (where
the request contained "Accept-Encoding: gzip, deflate") emitted by .svc wcf services.
On
the client, I've followed
the instructions here and here on how to inject this header into
the web request: "Accept-Encoding: gzip, deflate".
Fiddler2 shows
the response is binary and not plain old Xml.
The client crashes with an exception which basically says there's no Xml header, which ofcourse is true.
In my IClientMessageInspector,
the app crashes before AfterReceiveReply is called.
Some further notes:
(1) I can't change
the WCF service or
client as they are supplied by a 3rd party. I can however attach behaviors and/or message inspectors via configuration if this is
the right direction to take.
(2) I don't want to compress/uncompress just
the soap body, but
the entire message.
Any ideas/solutions?
* SOLVED *
It was not possible to write a WCF extension to achieve these goals. Instead I followed this CodeProject article which advocate a helper class:
public class CompressibleHttpRequestCreator : IWebRequestCreate
{
public CompressibleHttpRequestCreator()
{
}
WebRequest IWebRequestCreate.Create(Uri uri)
{
HttpWebRequest httpWebRequest =
Activator.CreateInstance(typeof(HttpWebRequest),
BindingFlags.CreateInstance | BindingFlags.Public |
BindingFlags.NonPublic | BindingFlags.Instance,
null, new object[] { uri, null }, null) as HttpWebRequest;
if (httpWebRequest == null)
{
return null;
}
httpWebRequest.AutomaticDecompression =DecompressionMethods.GZip |
DecompressionMethods.Deflate;
return httpWebRequest;
}
}
and also, an addition to
the application configuration file:
<configuration>
<system.net>
<webRequestModules>
<remove prefix="http:"/>
<add prefix="http:"
type="Pajocomo.Net.CompressibleHttpRequestCreator, Pajocomo" />
</webRequestModules>
</system.net>
</configuration>
What seems to be happening is that WCF eventually asks some factory or other deep down in system.net to provide an HttpWebRequest instance, and we provide
the helper that will be asked to create
the required instance.
In
the WCF
client configuration file, a simple basicHttpBinding is all that is required, without
the need for
any custom extensions.
When
the application runs,
the client Http request contains
the header "Accept-Encoding: gzip, deflate",
the server returns a gzipped web response, and
the client transparently decompresses
the http response before handing it over to WCF.
When I tried to apply this technique to Web Services I found that it did NOT work. Although
the helper class was executed in
the same was as when used by
the WCF
client,
the http request did not contain
the "Accept-Encoding: ..." header.
To make this work for Web Services, I had to edit
the Web Proxy class, and add this method:
protected override System.Net.WebRequest GetWebRequest(Uri uri)
{
System.Net.HttpWebRequest rq = (System.Net.HttpWebRequest)base.GetWebRequest(uri);
rq.AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate;
return rq;
}
Note that it did not matter whether
the CompressibleHttpRequestCreator and block from
the application config file were present or not. For web services, only overriding GetWebRequest in
the Web Service Proxy worked.
