WCF / ASMX :: Expose A Method To The Silverlight Client?

I'm having trouble exposing a method to a silverlight client from a WCF service although I can expose properties.

My WCF service has a LoadDeal method which returns a Deal object

public Deal LoadDeal(int dealerId)
{
Deal d = new Deal();
d.LoadDeal(dealerId);
return d;

[Code]....

This works fine and the Refernce property can be accessed from the silverlight client.

But when I try to expose a method such as the CancelEdit method below, I can't find a way to expose this method to the silverlight client:

public void CancelEdit()
{
//Add logic to cancel changes here.
}

I've tried adding the DataMember annotation but the compiler complains. I've re-compiled without an annotation and then updated the service reference but nothing seems to be working.