Created attachment 2282 [details]
Test Project and WSDL
When a web service uses custom Soap headers, the Microsoft .NET implementation of SoapExtension.ProcessMessage populates the message.Headers list during the AfterDeserialize stage. In the Mono implementation, no headers are listed.
Attached is a test project with WSDL. Running this project in Visual Studio and MonoDevelop reflects this difference in behavior.
-> class libs.