Command with navigation to another page - xamarin.forms

Question

i need to redirect to another page in ViewModel after performing some action. I have button and set my command, however if i load the page fort the first time then i get an error "Please use navigation page" application fails and i start it again and try to load the page and it works, but if i delete the app from emulator and try all over again i have the same process.
public ICommand FilterItemsCommand { get; private set; }
public FilterArticlesForPurchaseViewModel()
: base()
{
Task.Run(async () => await LoadAllDataForArticlesAndCategories()).Wait();
FilterItemsCommand = new Command(async () => await FilterItems());
}
private async Task FilterItems()
{
await Application.Current.MainPage.Navigation.PushAsync(new ArticlesForPurchaseFiltered());
}
App
MainPage = new NavigationPage(GetMainPage());
I have also tried this
Application.Current.MainPage = new NavigationPage(new ArticlesForPurchaseFiltered());
But then i cant go back to previous page and if i use android back button the application fails
BTW i am using master detail

Answer 1

You can add INavigation navigation to your ViewModel's constructor like following code.
public ItemsViewModel(INavigation navigation)
{
Title = "Browse";
Items = new ObservableCollection<Item>();
LoadItemsCommand = new Command(async () => await ExecuteLoadItemsCommand());
FilterItemsCommand = new Command(() => { navigation.PushModalAsync(new Page1()); });
MessagingCenter.Subscribe<NewItemPage, Item>(this, "AddItem", async (obj, item) =>
{
var newItem = item as Item;
Items.Add(newItem);
await DataStore.AddItemAsync(newItem);
});
}
When you binding the viewmodel, you can add the attribute like following code.
public ItemsPage()
{
InitializeComponent();
BindingContext = viewModel = new ItemsViewModel(Navigation);
}
If you want to achieve the navigation in the viewModel, you can use
// this way you need add `MainPage =new NavigationPage( new MainPage());` in app.xaml.cs
navigation.PushAsync(new Page1());
// this way you do not need `MainPage =new NavigationPage( new MainPage());` in //app.xaml.cs, just used it directly
navigation.PushModalAsync(new Page1());