How do I get a value from an XML web service in C#?

Question

In C#, if I need to open an HTTP connection, download XML and get one value from the result, how would I do that?

For consistency, imagine the webservice is at www.webservice.com and that if you pass it the POST argument fXML=1 it gives you back

<xml><somekey>somevalue</somekey></xml>

I'd like it to spit out "somevalue".

Answer 1

I think it will be useful to read this first:

Creating and Consuming a Web Service (in .NET)

This is a series of tutorials of how web services are used in .NET, including how XML input is used (deserialization).