why does my ObservableCollection not filter

Question

i have a WPF desktop app.

I load an ObservableCollection with a list of objects.

I use the ICollectionView object to 'wrap' a filter around this ObservableCollection .

I set the filter and refresh but it does nto work so:

public class DataFilters : ViewModelBase
{
    private ICollectionView _UserMappedRolesView { get; set; }

    private ObservableCollection<UserMappedRoles> _UserMappedRoles;
    public ObservableCollection<UserMappedRoles> UserMappedRoles
    {
        get
        {
            _UserMappedRolesView = CollectionViewSource.GetDefaultView(_UserMappedRoles);
            _UserMappedRolesView.Filter = UserMappedRolesFilter;
            _UserMappedRolesView.Refresh();
            return _UserMappedRoles;
        }
        set
        {
            _UserMappedRoles = value;
        }
    }

    public void LoadUserMappedRoles()
    {
        var baseData = InformedWorkerBusinessService.UserMappedRoles.Get();
        var modelData =
            from data in baseData
            select new UserMappedRoles
            {
                Enabled = 1,
                Login = data.Login,
                UserMappedRolesRef = data.UserMappedRolesRef,
                UserRoleRef = data.UserRoleRef

            };
        _UserMappedRoles = new ObservableCollection<UserMappedRoles>(modelData);
    }
    public string Login { get; set; }
    private bool UserMappedRolesFilter(object item)
    {
        UserMappedRoles UserMappedRole = item as UserMappedRoles;

        if (UserMappedRole.Login== Login)
        {
            return true;
        }
        else
        {
            return false;
        }
    }
}

and my test script:

UI.InformedWorkerViewModel.Models.HeartBeat VM = new UI.InformedWorkerViewModel.Models.HeartBeat();
VM.CommonData.DataFilters = new UI.InformedWorkerViewModel.Models.DataFilters();
VM.CommonData.DataFilters.LoadUserMappedRoles();
var data = VM.CommonData.DataFilters.UserMappedRoles;
VM.CommonData.DataFilters.Login = "David";
var filtered = VM.CommonData.DataFilters.UserMappedRoles;

I know my data only contains oUserMappedRoles where the Login name is 'Andy' so, by setting the Login filter name to 'David' I expect to get no records back.

I have set breakpoints everywhere and everyline of code gets 'hit'.

Have I (obviously) implemented this wrong?

Thanks

Answer 1

It is the ICollectionView that gets filtered, not the ObservableCollection.

So you should bind to the ICollectionView property:

<ListBox ItemsSource="{Binding UserMappedRolesView}" DisplayMemberPath="Login" />

...or look for the filtered items in this one:

var filtered = VM.CommonData.DataFilters.UserMappedRolesView;

You also need to refresh the CollectionView whenever you want to re-apply the filter, i.e. whenever your Login property is set to a new value. Something like this:

public class DataFilters : ViewModelBase
{
    private ICollectionView _UserMappedRolesView;
    public ICollectionView UserMappedRolesView
    {
        get { return _UserMappedRolesView; }
        set { _UserMappedRolesView = value; NotifyPropertyChanged(); }
    }

    private ObservableCollection<UserMappedRoles> _UserMappedRoles;
    public ObservableCollection<UserMappedRoles> UserMappedRoles
    {
        get
        {
            return _UserMappedRoles;
        }
        set
        {
            _UserMappedRoles = value;
            NotifyPropertyChanged();
            UserMappedRolesView = CollectionViewSource.GetDefaultView(_UserMappedRoles);
            UserMappedRolesView.Filter = UserMappedRolesFilter;
            UserMappedRolesView.Refresh();
        }
    }

    public void LoadUserMappedRoles()
    {
        var baseData = InformedWorkerBusinessService.UserMappedRoles.Get();
        var modelData =
            from data in baseData
            select new UserMappedRoles
            {
                Enabled = 1,
                Login = data.Login,
                UserMappedRolesRef = data.UserMappedRolesRef,
                UserRoleRef = data.UserRoleRef

            };
        UserMappedRoles = new ObservableCollection<UserMappedRoles>(modelData);
    }


    private string _login;
    public string Login
    {
        get { return _login; }
        set { _login = value; _UserMappedRolesView.Refresh(); }
    }


    private bool UserMappedRolesFilter(object item)
    {
        UserMappedRoles UserMappedRole = item as UserMappedRoles;
        if (UserMappedRole.Login == Login)
        {
            return true;
        }
        else
        {
            return false;
        }
    }
}