Data-binded value won't get updated on UI

Question

I have a class called Commander and it have a property called CurrentRound and it gets updated every few seconds internally. I'm using CommunityToolkit.MVVM and In my viewmodel I declared an observable property called CurrentRound and in the constructor of my viewmodel I did this currentRound = _commander.CurrentRound;.

The strange thing is that when I put a breakpoint in my Commander class and pause the program, I can see the updated value in my xaml file(view) but not on the actual UI.

Commander Class:

    public partial class Commander
    {
        private readonly Communication communication;
        public Commander(Communication communication) 
        {
            this.communication = communication;
            ThreadStart work = this.NameOfMethodToCall;
            Thread thread = new Thread(work);
            thread.Start();
        }
        private async void NameOfMethodToCall()
        {
            while(true)
            {
                await Task.Delay(10000);
                Console.WriteLine("hey I'm the second thread!");
                CurrentRound = GetCurrentRound();
            }
        }
        public int CurrentRound { get; private set; } = 1;
   }

ViewModel:

   public partial class ParametersViewModel: ObservableObject
    {
        public ParametersViewModel(Commander commander, ...)
        {
            _commander = commander;
            currentRound = _commander.CurrentRound;
            ...
        }
        private readonly Commander _commander;
        ...

        [ObservableProperty]
        int currentRound;
        ...
   }

View:

<Label
   Text="{Binding CurrentRound, StringFormat='Current Round = {0}'}"
   HorizontalOptions="Center"
   FontAttributes="Bold"
   FontSize="Body"/>
...

UPDATE:

Still having the same issue!

ViewModel:

public partial class ParametersViewModel: ObservableObject
{
   ...
   [ObservableProperty]
   Commander myCommander;
   ...
}

View:

<Label
   Text="{Binding MyCommander.CurrentRound, ...

SECOND UPDATE:

This update solved my issue but I should make my Commander class inherits from ObservableObject and make its CurrentRound property an ObservableProperty, but when using MVVM design pattern I should not worry about UI in the models and business logic, but if I do this, I should care about UI bindings in the models right? isn't there a better ways of doing this?

Commander Class:

    public partial class Commander: ObservableObject
    {
        ...
        [ObservableProperty]
        int currentRound = 1;
        ...
   }

Can you tell me which one are you setting as BindingConetxt ParametersViewModel or Commander class? — Prashant Rajput, Dec 28 '22 at 09:12
Why does your VM have a copy of the property instead of just binding to the property on the Commander class? — Jason, Dec 28 '22 at 09:14
@Jason is that a copy? I thought it's a reference. you mean something like this `"{Binding MyCommander.CurrentRound}"`? — Mahyar Shokraeian, Dec 28 '22 at 09:35
Yes, like that. But your VM will need to have a public property MyCommander. `int` is a value type, not an object — Jason, Dec 28 '22 at 09:43
@Jason I did it but still having the same issue. (I've added the updated results in my question) — Mahyar Shokraeian, Dec 28 '22 at 09:48
@Jason you mean I should make my `Commander` class inherits from `ObservableObject` and make its `CurrentRound` property an `ObservableProperty`? I thought when using MVVM design pattern I should not worry about UI in the models and business logic, but if I do what you are saying, I should care about UI bindings in the models right? isn't there a better ways of doing this? — Mahyar Shokraeian, Dec 28 '22 at 12:08
the VM/Model should be agnostic about who is consuming it. Raising an event when a property changes does not violate this - the decision on whether to subscribe to the event and what to do when it fires is up to the subscriber. — Jason, Dec 28 '22 at 14:54

score 0 · Answer 1 · answered Dec 29 '22 at 12:01

Just want to point out something.

Considering:

and in the constructor of my viewmodel I did this currentRound = _commander.CurrentRound

And:

[ObservableProperty]
int currentRound;

currentRound is a field. CurrentRound is a property.

Setting fields does not call code. Setting properties does.

All the problems you had, comes from no following naming conventions. Property A has field _a, not a.

Data-binded value won't get updated on UI

1 Answers1