title: Silverlight and push notifications
body: <p>I am creating a Silverlight 2 user interface to a remote instrument. There are two concurrent users at different sites interacting with the instrument (operator at the instrument and remote scientist) and any number of observer users not interacting with it, just watching. However, whenever one of the two active users changes something these changes must be immediately reflected in the UIs of all users, e.g. panning or zooming an image or annotating or selecting part of an image, adding items to a collection displayed in a listbox. Within the client I use observable collections which easily reflect changes made by that user, but it is harder seeing changes made by another user. I can poll for changes from each client but something like push notifications would be better. I have extensively Googled for examples but not found anything which is quite what I need. There are all sorts of security issues with Silverlight interacting with WCF services which mean many potential examples just don't work. I have essentially run out of time on this project and need help fast. Does anyone have any suggestion of a suitable simple example which illustrates how to do this? I am an experienced developer but have had to teach myself Silverlight and WCF services and there is noone in my area who knows anything about these. Even tho' I have done a fair amount of ASP.NET work I am not a web/Javascript guru. Thanks.</p>