Reflection, WCF Web service, LoadFrom Assembly oh my. Issues with Network Credentials - wcf

Question

I've created a WCF webservice, that can dynamically call other webservices/db connections with DLL's loaded with .LoadFile('from assembly'). Inside one of these assemblies, another webservice is called dynamically with a passed in network credential as follows:
WebClient client = new WebClient();
client.Credentials = this.networkCredential; //This credential is passed in
RequestStream requestStream = client.OpenRead(this.url);
//rest of code. The .OpenRead is giving 401 error (not authorized).
When I do this in debug mode from a test console application and creating the network credentials as follows:
NetworkCredential networkCredential = new NetworkCredential(<userid>,<password>,<domain>);
this works fine.
The failing code is providing networkcredentials as follows
System.Net.NetworkCredential networkCredential = System.Net.CredentialCache.DefaultNetworkCredentials;
Any help would be greatly appreciated.

Answer 1

Unless you are using impersonation, DefaultNetworkCredentials attempts to use the credentials of the process running your ASP.NET website, not the credentials of the user accessing your site. In order to use the credentials of the user, you should wrap your call to the web services in an impersonation context.
var impersonationContext = HttpContext.Current.Request.User.Identity.Impersonate();
if(impersonationContext != null)
{
//call your webservice here. DefaultNetworkCredentials will be what you expect.
impersonationContext.Undo();
}
There are, of course, conditions. The user must be authenticated (can't be an anonymous user, unless the anonymous user also has access to your web service). Also, the code above is just an example - in production code there are quite a few other things to consider. Here is an msdn article that should help get you started.
FYI, the reason it works in development is most likely because your development server process runs as you, and since you have access to the web service, it succeeds.