CODEWITHSUNDEEP
c#.netsilverlightbing-maps
Morgan Herlocker
Morgan Herlocker

Reputation: 1483

Throttling an event from a control in Silverlight

I have a Silverlight app that utilizes the Bing Maps control. Data loads when ever the maps view stops changing. I saw an example where someone used the ASP.Net version of the control and was able to acheive this. Is this same thing possible in Silverlight? 

Microsoft.Maps.Events.addThrottledHandler(map, 'viewchangeend', UpdatePOIData, 250);

Upvotes: 0

Views: 357

Answers (3)

Gary Wood
Gary Wood

Reputation: 11

To get around the Invalid cross-thread access ( UnauthorizedAccessExcecption) while using Subscribe function error you'll get using this code.

Use the following:

using System.Reactive.Concurrency;
using System.Reactive.Linq;

var observable = Observable.FromEventPattern<MapEventArgs>(
                    handler => MyMap.ViewChangeEnd += handler,
                    handler => MyMap.ViewChangeEnd -= handler);
observable.Throttle(TimeSpan.FromSeconds(2)).ObserveOn(DispatcherScheduler.Current).Subscribe(ev => MyMap_ViewChangeEnd(ev.Sender, ev.EventArgs));

You have to add the ObserveOn(DispatcherScheduler.Current) to make it work. And add references for System.Reactive.Core, System.Reactive.Interfaces, System.Reactive.Linq and System.Reactive.Windows.Threading.

Upvotes: 1

Gingemonster
Gingemonster

Reputation: 927

rx (unless Im behind) is not yet built into silverlight and seems a little overkill to have the client download all the rx dll just for throttling unless you are going to use it extensively.

At its simplest create your own throttling class using a dispatchtimer which takes the initial call waits x seconds and then checks if another call has come in since before executing your action.

Sorry I dont have any code to hand

Upvotes: 2

Thomas Levesque
Thomas Levesque

Reputation: 292405

You could do it with Reactive Extensions. The Throttle method exists for this purpose:

var observable =
    Observable.FromEventPattern<MapEventArgs>(
        handler => map.ViewChangeEnd += handler,
        handler => map.ViewChangeEnd -= handler);

observable.Throttle(TimeSpan.FromSeconds(1))
          .Subscribe(ev => map_ViewChangeEnd(ev.Sender, ev.EventArgs));


...

void map_ViewChangeEnd(object sender, MapEventArgs e)
{
    ...
}

(untested)

Upvotes: 1

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