calling webservice only once from viewmodel

[Erik de Hair]

Hi,

I have to call I web service from a view model but, when opening the 
view model, the call to the web service is called twice. It doesn't 
matter if the call is in de viewmodelinit or in some other method. May 
be there's some way to track the state of the view model and let whether 
or not the call is executed depend on that?

The web service is fetching data, triggered by an action in the view 
model, for the same view model. Do I always have to return a new view 
model with the fetched data in it or can I use the data from the fetch 
method and return the same view model?

Thanks,
Erik