Invoking web service methods from code-behind

The application on which I am working has a web service exposing various methods. Most of these methods use WebOperationContext.Current to set headers up to prevent cacheing. This works fine when the service methods are consumed in AJAX via the generated proxy, but when I attempt to do the same thing fr开发者_如何学JAVAom code-behind, WebOperationContext.Current is null.

Can anyone tell me how to confer appropriate call context on the method invocation?