json ihttpmodule compression - json

Question

I wrote an IHttpModule that compress my respone using gzip (I return a lot of data) in order to reduce response size.
It is working great as long as the web service doesn't throws an exception.
In case exception is thrown, the exception gzipped but the Content-encoding header is disappear and the client doesn't know to read the exception.
How can I solve this? Why the header is missing? I need to get the exception in the client.
Here is the module:
public class JsonCompressionModule : IHttpModule
{
public JsonCompressionModule()
{
}
public void Dispose()
{
}
public void Init(HttpApplication app)
{
app.BeginRequest += new EventHandler(Compress);
}
private void Compress(object sender, EventArgs e)
{
HttpApplication app = (HttpApplication)sender;
HttpRequest request = app.Request;
HttpResponse response = app.Response;
try
{
//Ajax Web Service request is always starts with application/json
if (request.ContentType.ToLower(CultureInfo.InvariantCulture).StartsWith("application/json"))
{
//User may be using an older version of IE which does not support compression, so skip those
if (!((request.Browser.IsBrowser("IE")) && (request.Browser.MajorVersion <= 6)))
{
string acceptEncoding = request.Headers["Accept-Encoding"];
if (!string.IsNullOrEmpty(acceptEncoding))
{
acceptEncoding = acceptEncoding.ToLower(CultureInfo.InvariantCulture);
if (acceptEncoding.Contains("gzip"))
{
response.AddHeader("Content-encoding", "gzip");
response.Filter = new GZipStream(response.Filter, CompressionMode.Compress);
}
else if (acceptEncoding.Contains("deflate"))
{
response.AddHeader("Content-encoding", "deflate");
response.Filter = new DeflateStream(response.Filter, CompressionMode.Compress);
}
}
}
}
}
catch (Exception ex)
{
int i = 4;
}
}
}
Here is the web service:
[WebMethod]
public void DoSomething()
{
throw new Exception("This message get currupted on the client because the client doesn't know it gzipped.");
}
I appriciate any help.
Thanks!

Answer 1

Even though it's been a while since you posted this question, I just had the same issue and here's how I fixed it:
In the Init() method, add a handler for the Error event
app.Error += new EventHandler(app_Error);
In the handler, remove Content-Type from the Response headers and set the Response.Filter property to null.
void app_Error(object sender, EventArgs e)
{
HttpApplication httpApp = (HttpApplication)sender;
HttpContext ctx = HttpContext.Current;
string encodingValue = httpApp.Response.Headers["Content-Encoding"];
if (encodingValue == "gzip" || encodingValue == "deflate")
{
httpApp.Response.Headers.Remove("Content-Encoding");
httpApp.Response.Filter = null;
}
}
Maybe there's a more elegant way to do this but did the trick for me.