private void ExecuteHeaderClickCommand(ContinentViewModel item)
 {
     item.Expanded = !item.Expanded;
 }
        private async Task ExecuteLoadDataCommand()
        {
            Country China = new Country("China", "CHN", "china");
            Country Japan = new Country("Japn", "JPN", "japan");
            Country Korea = new Country("Korea", "KOR", "korea");

            var Germany = new Country("Germany", "GEU", "germany");
            var France  = new Country("France", "FRA", "france");
            var UK      = new Country("United Kingdom", "GBR", "england");
            var Italia  = new Country("Italia", "ITA", "italia");

            var Arg    = new Country("Argentina", "ARG", "argentina");
            var Brazil = new Country("Brazil", "BRA", "brazil");
            var Col    = new Country("Colombia", "COL", "colombia");

            var Egypt   = new Country("Egypt", "EGY", "egypt");
            var Morocco = new Country("Morocco", "MAR", "morocco");

            Continent Asia = new Continent()
            {
                Name = "Asia"
            };

            Asia.Countries.Add(China);
            Asia.Countries.Add(Japan);
            Asia.Countries.Add(Korea);

            Continent Europa = new Continent()
            {
                Name = "Europa"
            };

            Europa.Countries.Add(Germany);
            Europa.Countries.Add(France);
            Europa.Countries.Add(UK);
            Europa.Countries.Add(Italia);

            Continent SA = new Continent()
            {
                Name = "South American"
            };

            SA.Countries.Add(Arg);
            SA.Countries.Add(Brazil);
            SA.Countries.Add(Col);

            Continent Africa = new Continent()
            {
                Name = "Africa"
            };

            Africa.Countries.Add(Morocco);
            Africa.Countries.Add(Egypt);

            var AsiaViewModel   = new ContinentViewModel(Asia);
            var EuropaViewModel = new ContinentViewModel(Europa);
            var SAViewModel     = new ContinentViewModel(SA);
            var AfricaViewModel = new ContinentViewModel(Africa);

            List.Add(AsiaViewModel);
            List.Add(EuropaViewModel);
            List.Add(SAViewModel);
            List.Add(AfricaViewModel);
        }