How to search items in CollectionView - xamarin.forms

Question

I have an ObservableRangeCollection that consists of a few items. How can I conduct a search in the ViewModel of the Page?
Edit:
ObservableCollection in ViewModel:
private ObservableRangeCollection<Smetka> _smetki = new ObservableRangeCollection<Smetka>();
public ObservableRangeCollection<Smetka> Smetki
{
get { return _smetki; }
set { SetProperty(ref _smetki, value); }
}
And this is the CollectionView in the View:
<CollectionView ItemsSource="{Binding Smetki}" BackgroundColor="{DynamicResource SecondaryColor}"
VerticalScrollBarVisibility="Never" HorizontalScrollBarVisibility="Never"
SelectionMode="Single" SelectionChangedCommand="{Binding LaunchDetailPage}"
SelectedItem="{Binding SelectedSmetka}" Grid.Row="1">
</CollectionView>
I have been searching for a VM search example for a while now. I would really appreciate it if someone could provide me with one.
Edit 2:
This is what the app looks like normally.
When Search Criteria is given the ObservableRangleCollection should display only the Smetkas, who meet the Criteria.
After removing the Search Criteria it should display all the Smetkas, who meet the new criteria. If the String is empty or whitespace it should display all of them.

Answer 1

Do you mean you want to retrieve the item from your list ?
If yes,just use LINQ,for example:
public class PLU
{
public int ID { get; set; }
public string name { get; set; }
public double price { get; set; }
public int quantity {get;set;}
}
public static ObservableCollection<PLU> PLUList = new ObservableCollection<PLU>();
retrieve like:
PLU item = PLUList.Where(z => z.ID == 12).FirstOrDefault();
Update:
string filter = "9";//the filter you input
var searchItems = new ObservableCollection<Smetka>(Smetki.Where((smetka) => smetka.Id.Contains(filter))); // Assuming the property is Id.
then you could replace the Smetki with searchItems .