I have an old application that uses the classic Web Service Proxy to interact with a Java Web Service. A while back the Web Service hoster decided to require a custom HTTP header to be sent with each request in order to access the service - otherwise the requests are thrown out outright (looks like this is some sort of router requirement). Regardless of what the reason I need to inject a custom HTTP header into the request.

Is there any way to interact with the actual Http client to do things like add custom headers?

You should be able to do this by overriding the GetWebRequest method of the proxy class in a partial class in a separate file. After calling the base class method, you should be able to modify the returned HttpWebRequest however you like, then return it from the method:

public partial class MyServiceProxy {     protected override WebRequest GetWebRequest(Uri uri) {         HttpWebRequest request = (HttpWebRequest) base.GetWebRequest(uri);         // do what you will with request.         return request;     } }