Query Web Service for list of Messages?

Question

Is there a straightforward way to query a web service to see which messages it supports? The C# .NET application I'm working on needs to be able to handle an older version of the web service, which does not implement the message I'm trying to send. The web service does not expose a version number, so Plan B is to see if the message is defined.

I'm assuming I can just make an HTTP request for the WSDL and parse it, but before I go down that path, I want to make sure there's not a simpler approach.

Update: I've decided to get the WSDL and get messages directly. Here's the rough draft for getting all the messages:

HttpWebRequest webRequest = (HttpWebRequest) WebRequest.Create( "http://your/web/service/here.asmx?WSDL" );
webRequest.PreAuthenticate = // details elided
webRequest.Credentials = // details elided
webRequest.Timeout = // details elided
HttpWebResponse webResponse = (HttpWebResponse) webRequest.GetResponse();

XPathDocument xpathDocument = new XPathDocument( webResponse.GetResponseStream() );
XPathNavigator xpathNavigator = xpathDocument.CreateNavigator();

XmlNamespaceManager xmlNamespaceManager = new XmlNamespaceManager( new NameTable() );
xmlNamespaceManager.AddNamespace( "wsdl", "http://schemas.xmlsoap.org/wsdl/" );

foreach( XPathNavigator node in xpathNavigator.Select( "//wsdl:message/@name", xmlNamespaceManager ) )
{
    string messageName = node.Value;
}

Answer 1

I'm pretty sure WSDL is the way to do this.

Answer 2

Parsing the WSDL is probably the simplest way to do this. Using WCF, it's also possible to download the WSDL at runtime, essentially run svcutil on it through code, and end up with a dynamically generated proxy that you can check the structure of. See http://blogs.msdn.com/vipulmodi/archive/2006/11/16/dynamic-programming-with-wcf.aspx for an example of a runtime-generated proxy.