Compression response filter fails on breeze.js Metadata call - filter

Question

I have an http module where I'm adding a response filter below for compression. This works for all API calls except for 1, the call to MetaData. If I remove the [BreezeController] decoration it works fine. I think it has to do with action filter attribute that converts the string return type into an HttpResponse return type with string content.
The error I'm getting is " Exception message: The stream state of the underlying compression routine is inconsistent."
I've done some testing where a method thats defined to return an HttpResponse works fine. So I think its the scenario where the method is defined to return string, and then the action filter changes it to HttpResponse at runtime.
Any ideas how I can get this to work?
Here's the response filter being added in BeginRequest:
HttpApplication app = (HttpApplication)sender;
// Check the header to see if it can accept compressed output
string encodings = app.Request.Headers.Get("Accept-Encoding");
if (encodings == null)
return;
Stream s = app.Response.Filter;
encodings = encodings.ToLower();
if (encodings.Contains("gzip"))
{
app.Response.Filter = new GZipStream(s, CompressionMode.Compress);
app.Response.AppendHeader("Content-Encoding", "gzip");
}

Answer 1

Don't know the specifics of what you're doing but I know that the [BreezeController] attribute strips out filters and adds back just the ones that breeze wants.
One approach might be to define a separate controller (ModelMetadataController) that only serves the metadata. This controller doesn't have the [BreezeController] attribute; it's a plain old Web API controller.
Then you create a "Breeze controller" (ModelController) with all of the usual methods except the Metadata method.
You call the metadata controller from the client during app launch via MetadataStore.fetchMetadata just to get metadata.
Once you have populated a metadataStore in this fashion, you use it in your EntityManager which sends query and save requests to the "real" Web API data controller.
The client code might look something like this:
var ds = new breeze.DataService({
serviceName: 'breeze/Model' // the breeze query & save controller
});
var ms = new MetadataStore({
namingConvention: breeze.NamingConvention.camelCase, // assuming that's what you want
});
ms.addDataService(ds); // associate the metadata-to-come with the "real" dataService
var manager = new breeze.EntityManager({
dataService: ds,
metadataStore: ms
});
// the fun bit: fetch the metadata from a different controller
var promise = ms.fetchMetadata('breeze/ModelMetadata') // the metadata-only controller!
return promise; // wait on it appropriately