Trigger an action to start after X milliseconds

Question

I'm developing a Xamarin Forms mobile app, which has a page containing a SearchBar, a ListView, and Map control. The list view contains a list of addresses, which are reflected as pins on the map.

As the user types in the SearchBar, the ListView is automatically updated (through ViewModel binding). The ViewModel method that filters the datasource for the list looks something like this...

void FilterList()
{
    listDataSource = new ObservableCollection<location>(
        locationData.Where(l => l.Address.Contains(searchBar.Text))
    );

    // ***** Now, update the map pins using the data in listDataSource
}

I want to update the Map as the ListView is filtered, but not on EVERY keypress as that could happen multiple times a second. Essentially, I want a "rolling pause" in each FilterList event before the Map is updated. In pseudo-code...

    // ***** Now, update the map pins using the data in listDataSource
    if (a previously-requested map update is pending)
    {
        // Cancel the pending map update request
    }

    // Request a new map update in 1000ms using [listDataSource]

It's possible to do this using the Stopwatch class, which is available in Portable Class Libraries, but I suspect there's a cleaner/better way to accomplish this using Tasks.

Can anyone suggest a "cleverer" PCL-compatible way to do this?

Answer 1

The problem with simple delays is that you can get a bunch of events queued up for when the delay expires. You can add logic to throw away the events that were raised while the delay was running. If you want to declare the logic at a higher level, you can use Reactive Extensions.