How to call invoke operation on domain service?

I have silverlight business application. I added an invoke method to my AuthenticationService class that returns bool.

How do I call this and get the result from the 开发者_运维问答client?

http://msdn.microsoft.com/en-us/library/ee707370(v=vs.91).aspx#Y1804

 var authCtx = new AuthenticationContext();
            authCtx.HasAccess1(io => {
                HasAccess1 = io.Value;
            }, null);