WPF Loose binding when filtering a list-CodePudding

I have a list of users below:

public ObservableCollection<User> Users
   {
     get;
     private set;
   }

And in the XAML file, I am binding Users to the grid control

<dxg:GridControl x:Name="grid" 
     ItemsSource="{Binding Users}"
     SelectedItem="{Binding CurrentUser}"
     ...
     >
    <dxg:GridControl.Columns>
        <dxg:GridColumn FieldName="Name" Header="name" />
        <dxg:GridColumn FieldName="Mobile" Header="mobile"/>
    </dxg:GridControl.Columns>
</dxg:GridControl>

Until here everything is Ok and the binding works correctly.

Now I want to bind special users. for example, users where the length of their names is less than 5.

private ObservableCollection<TUserItem> usersVisible;
public ObservableCollection<User> UsersVisible
   {
       get
       {
           return Users.Where(u => u.name.Length < 5).ToObservableCollection();
       }

       set
       {
           usersVisible = value;
           OnPropertyChanged();
       }
}

but it doesn't work and the XAML grid control doesn't update.

If I return

return Users;

instead of

return Users.Where(u => u.name.Length < 5).ToObservableCollection();

everything is ok and the binding works correctly.

What's your suggestion?

Thanks

CodePudding user response：

If you look up the source code of the method ToObservableCollection, you will find out that it returns a new collection. So your binding now points to the old objects still and you will not see any change. I have created a repo of a WPF sample for you that you can run here:

Note that I have not used an observable collection, but a plain list. You can see a sample of an observable collection using collection view source in this answer on SO: Binding a CollectionViewSource to ObservableCollection