C# – How to correctly bind (update) a DataGrid with a CollectionViewSource

ccollectionviewsourcedatagridobservablecollectionwpf

I have a (WPF) DataGrid where I attach an ICollectionView as

XAML:

 <DataGrid x:Name="TodoList" ItemsSource="{Binding TodoItemsCollection}" DataContext="{Binding}" />

Constructor (Code behind)

 TodoItemsCollection = CollectionViewSource.GetDefaultView(Storage.TodoItems);
 TodoItemsCollection.Filter = TodoItemsFilter;

(Storage.TodoItems is an ObservableCollection)

TodoItemsCollection Property

 private ICollectionView _todoItemsCollection;
 public ICollectionView TodoItemsCollection
 {
     get { return _todoItemsCollection; }
     set 
     {
         if (_todoItemsCollection != value)
         {
             _todoItemsCollection = value;
             OnPropertyChanged("TodoItemsCollection");
         }
     }
 }

Storage.TodoItems is an ObservableCollection where a tracker adds, edits and removes items.
This changes should immediately be displayed in the DataGrid.

However, the problem is that all those changes are not reflected in the DataGrid (i.e. the DataGrid is not updated).
For example if I call TodoItemsCollection.Refresh(), nothing changes.
With a refresh button (only for testing purposes), I set the ItemsSource of the DataGrid to null and reset it (TodoItemsCollection = CollectionViewSource.GetDefaultView(Storage.TodoItems);).
This manual refresh displays the new/changed/removed items.
However, the filtering then doesn't work anymore.

I read about three dozens of blog posts and couldn't find a solution to my problems.
Usually, calling Refresh() or resetting the ItemsSource worked well for them.

Any suggestions are really much appreciated!!

Best Answer

in addition to liquidsnake786 answer - you can use the ObservableCollection instead of the ICollectionView and filtering/sorting will work just the same as long as you use CollectionViewSource.GetDefaultView(Storage.TodoItems).

the more important thing is that the Storage.TodoItems should just initialize once otherwise TodoItemsCollection = CollectionViewSource.GetDefaultView(Storage.TodoItems); have to be called every time a new Storage.TodoItems is created. simply use clear() add() and remove() to alter your Storage.TodoItems.

EDIT: the usual way:

-just create a OberservableCollection once (eg. within ctor). this collection will handle Add and Remove and notify the WPF ui.

this.MyCollection = new OberservableCollection<TodoItem>();

-your wrapped item "TodoItem" should implement INotifyPropertyChanged to notifiy changes/edits to WPF ui

-create you ICollectionView once(eg. within the ctor) like you did

 this.MyView = CollectionViewSource.GetDefaultView(MyCollection);
 this.MyView.Filter = TodoItemsFilter;

-alter your source collection with clear, add, remove

 this.MyCollection.Clear();
 foreach(var item in MyNewCollectionFromAnywhere)
 { this.MyCollection.Add(item);}
 this.MyView.Refresh();

-be sure that your datacontext and binding is right in xaml :) btw DataContext="{Binding}" makes no sense for me.

<DataGrid ItemsSource="{Binding MyView}"/>

Related Solutions

C# – Binding a WPF ComboBox to a custom list

You set the DisplayMemberPath and the SelectedValuePath to "Name", so I assume that you have a class PhoneBookEntry with a public property Name.

Have you set the DataContext to your ConnectionViewModel object?

I copied you code and made some minor modifications, and it seems to work fine. I can set the viewmodels PhoneBookEnty property and the selected item in the combobox changes, and I can change the selected item in the combobox and the view models PhoneBookEntry property is set correctly.

Here is my XAML content:

<Window x:Class="WpfApplication6.Window1"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="Window1" Height="300" Width="300">
<Grid>
    <StackPanel>
        <Button Click="Button_Click">asdf</Button>
        <ComboBox ItemsSource="{Binding Path=PhonebookEntries}"
                  DisplayMemberPath="Name"
                  SelectedValuePath="Name"
                  SelectedValue="{Binding Path=PhonebookEntry}" />
    </StackPanel>
</Grid>
</Window>

And here is my code-behind:

namespace WpfApplication6
{

    /// <summary>
    /// Interaction logic for Window1.xaml
    /// </summary>
    public partial class Window1 : Window
    {
        public Window1()
        {
            InitializeComponent();
            ConnectionViewModel vm = new ConnectionViewModel();
            DataContext = vm;
        }

        private void Button_Click(object sender, RoutedEventArgs e)
        {
            ((ConnectionViewModel)DataContext).PhonebookEntry = "test";
        }
    }

    public class PhoneBookEntry
    {
        public string Name { get; set; }

        public PhoneBookEntry(string name)
        {
            Name = name;
        }

        public override string ToString()
        {
            return Name;
        }
    }

    public class ConnectionViewModel : INotifyPropertyChanged
    {
        public ConnectionViewModel()
        {
            IList<PhoneBookEntry> list = new List<PhoneBookEntry>();
            list.Add(new PhoneBookEntry("test"));
            list.Add(new PhoneBookEntry("test2"));
            _phonebookEntries = new CollectionView(list);
        }

        private readonly CollectionView _phonebookEntries;
        private string _phonebookEntry;

        public CollectionView PhonebookEntries
        {
            get { return _phonebookEntries; }
        }

        public string PhonebookEntry
        {
            get { return _phonebookEntry; }
            set
            {
                if (_phonebookEntry == value) return;
                _phonebookEntry = value;
                OnPropertyChanged("PhonebookEntry");
            }
        }

        private void OnPropertyChanged(string propertyName)
        {
            if (PropertyChanged != null)
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
        public event PropertyChangedEventHandler PropertyChanged;
    }
}

Edit: Geoffs second example does not seem to work, which seems a bit odd to me. If I change the PhonebookEntries property on the ConnectionViewModel to be of type ReadOnlyCollection, the TwoWay binding of the SelectedValue property on the combobox works fine.

Maybe there is an issue with the CollectionView? I noticed a warning in the output console:

System.Windows.Data Warning: 50 : Using CollectionView directly is not fully supported. The basic features work, although with some inefficiencies, but advanced features may encounter known bugs. Consider using a derived class to avoid these problems.

Edit2 (.NET 4.5): The content of the DropDownList can be based on ToString() and not of DisplayMemberPath, while DisplayMemberPath specifies the member for the selected and displayed item only.

C# – How to update the GUI from another thread

The simplest way is an anonymous method passed into Label.Invoke:

// Running on the worker thread
string newText = "abc";
form.Label.Invoke((MethodInvoker)delegate {
    // Running on the UI thread
    form.Label.Text = newText;
});
// Back on the worker thread

Notice that Invoke blocks execution until it completes--this is synchronous code. The question doesn't ask about asynchronous code, but there is lots of content on Stack Overflow about writing asynchronous code when you want to learn about it.

Best Answer

Related Solutions

C# – Binding a WPF ComboBox to a custom list

C# – How to update the GUI from another thread

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