When collection changed in ObservableCollection add new entries to ReactiveList

[Max Reble]

Hi

I'm very new to ReactiveUI, and its quite hard for me to getting started. I have a ObservableCollection which getting filled from a TCP Model. When new data arrives, I want to create new Buttons inside an ItemsControl. It works the old way (with CollectionChanged) but I don't get it work with ReactiveUI. 

Could you may help me, by sending me to the right functions in reactiveUI or maybe by providing some sample code, I would be very pleased! 

The Idea:

public class ChooseMachineViewModel : ReactiveObject, IRoutableViewModel

{

public ReactiveList<Button> ButtonList { get; set; }

private Dictionary<ushort, Button> addressToButton;

public string UrlPathSegment => "ChooseMachine";

public IScreenTransportable HostScreen { get; }

IScreen IRoutableViewModel.HostScreen => HostScreen;

public ChooseMachineViewModel(IScreenTransportable screen)

{

HostScreen = screen;

//TODO: Make this Reactive!

//The ButtonList for an ItemsControl

ButtonList = new ReactiveList<Button>();

//The Dictonary for addresses -> Button

addressToButton = new Dictionary<ushort, Button>();

//The ObservableCollection filled by a TCP Server

HostScreen.Transporter.ControlUnitsStatus.CollectionChanged += ControlUnitsStatus_CollectionChanged;

}

private void ControlUnitsStatus_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)

{

if (e.NewItems != null)

{

foreach (WWSS.Message.CUStatus stat in e.NewItems)

{

TryAddButton(stat);//When new Status arrive, try to create new button

}

}

if (e.OldItems != null)

{

foreach (WWSS.Message.CUStatus stat in e.OldItems)

{

TryRemoveButton(stat);//When Status removed, try to remove the button

}

}

}

private bool TryAddButton(WWSS.Message.CUStatus status)

{

if (!addressToButton.ContainsKey(status.Address))//if the Address is already in the dictonary don't create a button

{

var but = new Button { Content = status.Address.ToString() };

addressToButton.Add(status.Address, but);

ButtonList.Add(but);

return true;

}

return false;

}

private void TryRemoveButton(WWSS.Message.CUStatus status)

{

if (addressToButton.ContainsKey(status.Address))

{

ButtonList.Remove(addressToButton[status.Address]);

addressToButton.Remove(status.Address);

}

}

}

Thanks in advance,

Max

[Valdimar Kristjánsson]

Hi Max,

How about something like this?

public class ChooseMachineViewModel : ReactiveObject

    {

        public IReactiveDerivedList<Button> ButtonList { get; set; }

        public ChooseMachineViewModel(ObservableCollection<CUStatus> source)

        {

            addressToButton = new Dictionary<ushort, Button>();

            ButtonList = source.CreateDerivedCollection(status => new Button { Content = status.Address.ToString() },

                                                        status => !ButtonList.Any(button => button.Content.ToString().Equals(status.Address.ToString())));

        }

    }

And a test:

    [TestClass]

    public class ChooseMachineViewModelTest

    {

        [TestMethod]

        public void TestAddingAndRemovingFromSource()

        {

            var source = new ObservableCollection<CUStatus>();

            var model = new ChooseMachineViewModel(source);

            Assert.AreEqual(source.Count, model.ButtonList.Count);

            source.Add(new CUStatus(65034));

            Assert.AreEqual(source.Count, model.ButtonList.Count);

            source.Clear();

            Assert.AreEqual(source.Count, model.ButtonList.Count);

            source.Add(new CUStatus(65034));

            Assert.AreEqual(source.Count, model.ButtonList.Count);

            source.Add(new CUStatus(65034));//insert a duplicate

            Assert.AreEqual(source.Count-1, model.ButtonList.Count);

            Assert.AreEqual(source.Count - 1, model.ButtonList.Count);

        }

    }

Cheers,

nisbus

[Valdimar Kristjánsson]

please remove the addressToButton thingy :)

[Max Reble]

Just... Wow... Okay I definitely have to stick to ReactiveUI, this is just beautiful and easy to understand. For me its like Spanish: I can listen very good to some one who is speaking Spanish, but talking is quite hard for me ;-) 

Thank you very much Valdimar!