Nsryjdtyk

I am building a screen for my app in xamarin.forms the caul is based on a tabbedpage which is built dynamically based on a list of objects which I get as a result of consuming a service.
After I call the method to consume the API that brings the list, I need to go through it based on certain data of it to fill an observable collection of viewmodels, which will be the tabs. The problem I have is that I do not know how to call the async method that consumes the API in a synchronized way so that the consumption of the API does not conflict with the operation of going through the list.
Then a fraction of the code of my ViewModel:

public MonitoringViewModel()

    {

        LoadThings();

        Tabs = new ObservableCollection<MonitoringTabsViewModel>();

        foreach (PcThing t in Things)

        {

            Tabs.Add(new MonitoringTabsViewModel(t.description));

        }

    }





    private async void LoadThings()

    {

        Things = new List<PcThing>(await App.WebApiManager.GetCustomerThinksAsync());

    }

What I get is that in xamarin live player the app after a few seconds go from the green signal to the red one without showing anything, and in the log of it I get this:
Target of GetEnumerator is null (NullReferenceException)

Since you are doing this in the constructor , I would try the following:

using System.Threading.Tasks;

The risk here is if you are not in control of the LoadThings completing, it can hang.

public MonitoringViewModel()

{

    var task = Task.Run(async () => { await LoadThings();}

    Task.WaitAll(task); //block and wait for task to complete

public async Task<List<PcThing>> LoadThings()

{

    return await App.WebApiManager.GetCustomerThinksAsync();

}

And in your ViewModel

Things = LoadThings().GetAwaiter().GetResult();