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Why is this ListView not changing with changes to the bound property?

Basic question from a novice. I've been stuck on this and have read through a lot of material and several similar questions on SO; hopefully not a completely duplicate question. I simplified the code as much as I know how to.
I'm trying to make the ListView show a filtered ObservableCollection) property (as the ItemsSource?), based on the selection in the ComboBox.
Specifically, which "meetings" have this "coordinator" related to it.
I'm not seeing any data errors in the output while it's running and debugging shows the properties updating correctly, but the ListView stays blank. I'm trying to avoid any code-behind on the View, there is none currently.
Thanks!
public class ViewModel : INotifyPropertyChanged
{
private ObservableCollection<Meeting> meetings;
public ObservableCollection<Meeting> Meetings
{
get
{
return meetings;
}
set
{
meetings = value;
OnPropertyChanged("ListProperty");
OnPropertyChanged("Meetings");
}
}
private string coordinatorSelected;
public string CoordinatorSelected
{
get
{
return coordinatorSelected;
}
set
{
coordinatorSelected = value;
Meetings = fakeDB.Where(v => v.CoordinatorName == CoordinatorSelected) as ObservableCollection<Meeting>;
}
}
private ObservableCollection<string> comboProperty = new ObservableCollection<string> { "Joe", "Helen", "Sven" };
public ObservableCollection<string> ComboProperty
{
get
{
return comboProperty;
}
}
private ObservableCollection<Meeting> fakeDB = new ObservableCollection<Meeting>() { new Meeting("Joe", "Atlas"), new Meeting("Sven", "Contoso"), new Meeting("Helen", "Acme") };
public ObservableCollection<Meeting> ListProperty
{
get
{
return Meetings;
}
}
public class Meeting
{
public string CoordinatorName { get; set; }
public string ClientName { get; set; }
public Meeting(string coordinatorName, string clientName)
{
CoordinatorName = coordinatorName;
ClientName = clientName;
}
}
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged(string propertyName)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
XAML:
<Window.Resources>
<local:ViewModel x:Key="VM"></local:ViewModel>
</Window.Resources>
<DockPanel DataContext="{StaticResource ResourceKey=VM}">
<ComboBox Margin="10" ItemsSource="{Binding ComboProperty}" SelectedItem="{Binding CoordinatorSelected}" DockPanel.Dock="Top"/>
<ListView Margin="10" ItemsSource="{Binding ListProperty, UpdateSourceTrigger=PropertyChanged}" DisplayMemberPath="ClientName"/>
</DockPanel>
Update:
This seems to show that the lambda is returning a Meeting object but the assignment to Meetings is failing. Is this an error in casting maybe?
Thanks again.

You always have to change a property's backing field before you fire a PropertyChanged event. Otherwise a consumer of the event would still get the old value when it reads the property.
Change the Meetings property setter like this:
public ObservableCollection<Meeting> Meetings
{
get
{
return meetings;
}
set
{
meetings = value;
OnPropertyChanged("ListProperty");
OnPropertyChanged("Meetings");
}
}

I believe I've found two solutions to the same problem. The error pointed out #Clemens was also part of the solution. The Meetings property problem is solved if I change ListProperty and Meetings to IEnumerable. Alternatively this approach without changing the type, which I believe invokes the collection's constructor with the filtered sequence as an argument.
set
{
coordinatorSelected = value;
var filteredList = fakeDB.Where(v => v.CoordinatorName == coordinatorSelected);
Meetings = new ObservableCollection<Meeting>(filteredList);
OnPropertyChanged("ListProperty");
}

Filter Method of ICollectionView and Properly Binding and ObservableCollection in MVVM

I'm getting stuck into MVVM in WPF and I have setup an ObservableCollection and an ICollectionView. The ICollectionView is set as the ItemsSource of a DataGrid, and the model is a type of Job.
I've setup getters and setter for both of the collections however when I am setting a Filter on the ICollectionView instead of the Job being filtered by the SearchString they're just replicated over and over again, leading me to believe that they way I have the collections setup is totally wrong.
Here is how the two collections are get/set:
public ObservableCollection<Job> AllJobs
{
get
{
foreach (var job in _allJobsList)
_allJobs.Add(job);
return _allJobs;
}
set
{
if (_allJobs == value) return;
OnPropertyChanged("AllJobs");
}
}
public ICollectionView AllJobsView
{
get
{
_allJobsView = CollectionViewSource.GetDefaultView(AllJobs);
return _allJobsView;
}
set
{
if (_allJobsView == value)
{
return;
}
_allJobsView = value;
OnPropertyChanged("AllJobsView");
}
}
Now I have a stringcalled SearchString that is bound to a TextBox.Text. When the text changes I do the following:
public string SearchString
{
get => _searchString;
set
{
if (_searchString == value) return;
_searchString = value;
FilterJobs();
OnPropertyChanged("SearchString");
}
}
private void FilterJobs()
{
AllJobsView.Filter = x =>
{
var viewJob = x as Job;
return viewJob != null && viewJob.Number.Contains(_searchString);
};
}
Now when the page first loads, there are the correct Jobs loaded into the DataGrid. However, as soon as the user types the Jobs are duplicated if the Job.Number does contain the SearchString. How am I able to setup the collections so that I can appropriately set a filter?

The problem is in the getter of your ObservableCollection. Every time you "get" the collection, you are adding every item to the collection all over again.
Your code:
get
{
foreach (var job in _allJobsList)
_allJobs.Add(job);
return _allJobs;
}
Instead, it should be:
get
{
return _allJobs;
}
The setter of your ObservableCollection is also missing the "setter" (private field = value) code:
set
{
if (value != _allJobs)
{
_allJobs = value;
OnPropertyChanged("AllJobs");
}
}
Your Property AllJobs would then be:
private ObservableCollection<Job> _allJobs;
public ObservableCollection<Job> AllJobs
{
get
{
return _allJobs;
}
set
{
if (value != _allJobs)
{
_allJobs = value;
OnPropertyChanged("AllJobs");
}
}
}
The initialization of your collection should be someplace else (and not in the getter of your property), like in the constructor of the ViewModel or/and in a method that a command calls after the user asks for a refresh of the collection.
For example, if your VieModel is called MyViewModel and your List<Job> is called _allJobsList, you can initialize your collection like so:
public MyViewModel()
{
//fill the _allJobsList first, getting from a database for example: _allJobsList = GetJobs();
//and then create an observable collection from that list
AllJobs = new ObservableCollection<Job>(_allJobsList);
}

Update ListcollectionView based on current item of other ListCollectionView

I want to Update ListCollectionView in a listbox each time the Item of another ListCollection gets selected.
I have 2 ListViewCollection, SceneCollectionView and ShotCollectionView. I want to have the SceneCollection filtered based on a property SceneNumber in ShotCollectionView, but I can get the ShotCollectionView to update when I go from one item to the other in SceneCollectionView.
This is my ViewModel
public class ShotListViewModel : NotifyUIBase
{
public ListCollectionView SceneCollectionView { get; set; }
private Scenes CurrentScene
{
get { return SceneCollectionView.CurrentItem as Scenes; }
set { SceneCollectionView.MoveCurrentTo(value); RaisePropertyChanged(); }
}
private ObservableCollection<Shot> _allShots = new ObservableCollection<Shot>();
public ObservableCollection<Shot> AllShots
{
get { return _allShots; }
set { _allShots = value; RaisePropertyChanged();}
}
private ListCollectionView _allShotsCollection;
public ListCollectionView AllShotsCollection
{
get
{
if (_allShotsCollection == null)
{
_allShotsCollection = new ListCollectionView(this.AllShots);
_allShotsCollection.Filter = IsSceneNumber;
}
return _allShotsCollection;
}
}
private bool IsSceneNumber(object obj)
{
if (obj as Shot != null
&& (obj as Shot).SceneNumber == (SceneCollectionView.CurrentItem as Scene).SceneNumber)
{
return true;
}
return false;
}
public ShotListViewModel()
{
SceneCollectionView = Application.Current.Resources["SceneCollectionView"] as ListCollectionView;
GetShotList(); //Populates the AllShots Observable collection.
AddShotCommand = new RelayCommand(AddShot);
FilterShotsCommand = new RelayCommand(AddShot);
}
What am I missing here to make it work or is it better to use ICollectionViewLiveShaping. but I have no idea how to implement that

I don`t understand what you tried to do, but lets talk on an example :
Lets say we have
ListBox1 binded to ListBox1Items and
ListBox2 binded to ListBox2Items.
if you want to filter the data from ListBox2 you have to filter ListBox2Items. How to do that ? Is simple : ListBox1 has a property SelectedItem which you can bind to --- lets say --- ListBox1SelectedItem. Every time when selection change, in the setter of the ListBox1SelectedItem you can trigger a filter on ListBox2Items.
Hope you understand what I`ve explained.

Binding List of Object to DataGrid

I'm trying to bind a list of objects to a DataGrid on the compact framework. This is what I have:
public class Order
{
//Other stuff
public Customer Customer
{
get { return _customer; }
}
}
public class Customer
{
//Other stuff
public string Address
{
get { return _address; }
}
}
Now I want to bind the DataGrid to a list of Order and display only certain properties (the customer's address is one of them):
List<Order> orders = MethodThatGetsOrders();
datagrid.DataSource = orders;
datagrid.TableStyles.Clear();
DataGridTableStyle ts = new DataGridTableStyle();
ts.MappingName = orders.GetType().Name; //This works OK
DataGridTextBoxColumn tb = new DataGridTextBoxColumn();
tb.MappingName = orders.GetType().GetProperty("Customer").GetType().GetProperty("Address").Name; //Throws NullRef
ts.GridColumnStyles.Add(tb);
datagrid.TableStyles.Add(ts);
How can I display the customer's address on the DataGridTextBoxColumn?
Thanks

I would form a viewmodel (or better an adapter) before having to mess around with bindings and get a flat model you can bind easily to:
public class OrderViewModel
{
private Order _order;
public string Address
{
get { return _order.Customer.Address; }
}
// similar with other properties
public OrderViewModel(Order order)
{
_order = order;
}
}
To generate the ViewModelList do:
List<OrderViewModel> viewModels = yourList.Select(m=> new OrderViewModel(m)).ToList();
And to bind simply:
YourGridView.Datasource = new BindingSource(viewModels, null);

Programmatically WPF listbox.ItemsSource update

I am doing a program like messenger that has all the contacts in a listbox with the relative states of the contacts.
Cyclic I get a xml with the contacts were updated over time, then updates the states within a class of binding called "Contacts".
The class Contacts has a filter to display only certain contacts by their state, "online, away, busy,.. " but not offline, for example ....
Some code:
public class Contacts : ObservableCollection<ContactData>
{
private ContactData.States _state = ContactData.States.Online | ContactData.States.Busy;
public ContactData.States Filter { get { return _state; } set { _state = value; } }
public IEnumerable<ContactData> FilteredItems
{
get { return Items.Where(o => o.State == _state || (_state & o.State) == o.State).ToArray(); }
}
public Contacts()
{
XDocument doc = XDocument.Load("http://localhost/contact/xml/contactlist.php");
foreach (ContactData data in ContactData.ParseXML(doc)) Add(data);
}
}
Update part:
void StatusUpdater(object sender, EventArgs e)
{
ContactData[] contacts = ((Contacts)contactList.Resources["Contacts"]).ToArray<ContactData>();
XDocument doc = XDocument.Load("http://localhost/contact/xml/status.php");
foreach (XElement node in doc.Descendants("update"))
{
var item = contacts.Where(i => i.UserID.ToString() == node.Element("uid").Value);
ContactData[] its = item.ToArray();
if (its.Length > 0) its[0].Data["state"] = node.Element("state").Value;
}
contactList.ListBox.ItemsSource = ((Contacts)contactList.Resources["Contacts"]).FilteredItems;
}
My problem is that when ItemsSource reassigns the value of the listbox, the program lag for a few seconds, until it has finished updating contacts UI (currently 250 simulated).
How can I avoid this annoying problem?
Edit:
I tried with Thread and after with BackgroundWorker but nothing is changed...
When i call Dispatcher.Invoke lag happen.
Class ContactData
public class ContactData : INotifyPropertyChanged
{
public enum States { Offline = 1, Online = 2, Away = 4, Busy = 8 }
public event PropertyChangedEventHandler PropertyChanged;
public int UserID
{
get { return int.Parse(Data["uid"]); }
set { Data["uid"] = value.ToString(); NotifyPropertyChanged("UserID"); }
}
public States State
{
get { return (States)Enum.Parse(typeof(States), Data["state"]); }
//set { Data["state"] = value.ToString(); NotifyPropertyChanged("State"); }
//correct way to update, i forgot to notify changes of "ColorState" and "BrushState"
set
{
Data["state"] = value.ToString();
NotifyPropertyChanged("State");
NotifyPropertyChanged("ColorState");
NotifyPropertyChanged("BrushState");
}
}
public Dictionary<string, string> Data { get; set; }
public void Set(string name, string value)
{
if (Data.Keys.Contains(name)) Data[name] = value;
else Data.Add(name, value);
NotifyPropertyChanged("Data");
}
public Color ColorState { get { return UserStateToColorState(State); } }
public Brush BrushState { get { return new SolidColorBrush(ColorState); } }
public string FullName { get { return Data["name"] + ' ' + Data["surname"]; } }
public ContactData() {}
public override string ToString()
{
try { return FullName; }
catch (Exception e) { Console.WriteLine(e.Message); return base.ToString(); }
}
Color UserStateToColorState(States state)
{
switch (state)
{
case States.Online: return Colors.LightGreen;
case States.Away: return Colors.Orange;
case States.Busy: return Colors.Red;
case States.Offline: default: return Colors.Gray;
}
}
public void NotifyPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
public static ContactData[] ParseXML(XDocument xmlDocument)
{
var result = from entry in xmlDocument.Descendants("contact")
select new ContactData { Data = entry.Elements().ToDictionary(e => e.Name.ToString(), e => e.Value) };
return result.ToArray<ContactData>();
}
}

I developed a similar software: a huge contact list with data (presence and other stuff) updating quite frequently.
The solution I used is different: instead of updating the whole itemssource everytime, that is quite expensive, implement a ViewModel class for each contact. The ViewModel class should implement INotifiyPropertyChanged.
At this point when you parse the XML, you update the ContactViewModel properties and this will trigger the correct NotifyPropertyChanged events that will update the correct piece of UI.
It might be expensive if you update a lot of properties for a lot of contacts at the same time, for that you can implement some kind of caching like:
contactViewModel.BeginUpdate()
contactViewModel.Presence = Presence.Available;
..... other updates
contactViewModel.EndUpdate(); // at this point trigger PropertyCHanged events.
Another point:
keep a separate ObservableCollection bound to the ListBox and never change the itemssource property: you risk losing the current selection, scrollposition, etc.
dynamically add/remove elements from the collection bound to the listbox.
Buon divertimento e in bocca al lupo :-)

Move the downloading and parsing of the contact status information to another thread.

The line where you assigning the ItemsSource I would put in another thread, but remember about invoking or you're gonna have irritating errors.