How to auto select first item?

[a44281071]

// source: 
SourceCache<CountryInfo, Guid> countryCache

// bindable collection:
[Bindable(true)]
ObservableCollectionExtended<CountryViewModel> CountryItems

// selected item:
[Bindable(true)]
CountryViewModel CurrentCountry

// bind
countryCache.Connect().Sort().Transform().ObserveOnDispatcher().Bind(CountryItems).Subscribe();
// then auto select first item default.
// warn, CountryItems is empty (can't wait for first data filling.)
CurrentCountry = CountryItems.FirstOrDefault(dd=>dd.Id == old_saved_id);

// xaml
<Combobox ItemsSource="{Binding CountryItems}" SelectedItem="{Binding CurrentCountry"/>

How to wait first data filling for CountryItems? And get any item.

[a44281071]

test is here:

https://github.com/a44281071/TestDynamicData/blob/8af90c3dc1f3362c88ec305a01c6f884169aa044/TestDynamicData/Views/SelectFirstItemViewModel.cs#L67

please open SelectFirstItemViewModel module view, select a item, close it to save.
then open it again.

[RolandPheasant]

There's a lot of options for selecting the first item. For example you can:

        private IDisposable CreateCountryBind()
        {
            var handle = dataAccessor.CountryCache.Connect()
                .Transform(dd => new CountryViewModel(dd))
                .Sort(SortExpressionComparer<CountryViewModel>.Ascending(p => p.Info.Name))
                .ObserveOnDispatcher()
                .Bind(CountryItems)
                .Subscribe();

            var selector = CountryItems.ToObservableChangeSet()
                .ToCollection()
                .Select(items => items.FirstOrDefault())
                .Where(vm => vm != null)
                .Take(1)  //Take 1 to run task once only
                .Subscribe(item =>
                {
                    CurrentCountry = item;
                });

            return new CompositeDisposable(handle, selector);
        }