I want to display a bunch of Objects i have created in a ListBox. My objects implement the INotifyPropertyChanged Interface.
I tried to use an ObservableCollection, which i have bound to a listbox Control (listbox1.DataContext = MyCollection)
But this does not exactly what i want to do, because the Listbox is not refreshed when one of the properties of one of my objects in MyCollection changes.
I have found this blogposting: http://sweux.com/blogs/psampaio/index.php/2009/04/13/creating-a-custom-observable-collection-in-wpf
is this realy the easyiest/only way to keep track of several objects?
I'm not sure, but have you tried using a datatemplate for your listbox items? like, a textbox that explicitly sets it's text to the appropriate binding.
Related
How do I add data to the WPF ListView items like Windows Forms?
Using databinding you can bind the itemssource to something like an observable collection then have your items added to that.
This approach makes it fairly easy to manipulate the data once you get used to databinding as long as you have INotifyPropertyChanged implemented your listview will update when you call OnPropertyChanged().
I have a listbox bound to a collection. I would like the ListBox to always reverse the order of the items. This handler--hooked up to the control's load event--works for the initial load, but not thereafter. Ive tried using the SourceUpdated event but that doesnt seem to work.
How do I maintain a constant active sort?
MyList.Items.SortDescriptions.Add(New SortDescription("Content", ListSortDirection.Descending))
How is the collection stored that supplies the items for the ListBox? It should be a collection that supports INotifyCollectionChanged. The framework provides ObservableCollection<T> which you can use.
In the constructor of your ViewModel (or wherever the collection lives), you then get the DefaultView for adding the SortDescription. The CollectionView is like a layer on top of your collection, which you can use to sort, group, filter, etc. the items without actually affecting the underlying data source. The framework creates a default one for you. To get a reference to it, you can use code similar to the following:
var collectionView = CollectionViewSource.GetDefaultView(Widgets);
if(collectionView == null)
return;
collectionView.SortDescriptions.Add(new SortDescription("Content", ListSortDirection.Descending));
With that in place, you should be able to add items to the ObservableCollection<T> and the sort order will be maintained.
If your source collection is a List<T> or some other collection that doesn't implement INotifyCollectionChanged, there is no way WPF can detect when an item is added. You need to use a collection that implements INotifyCollectionChanged, like ObservableCollection<T>.
Also, the items in your collection need to implement INotifyCollectionChanged so that changes to the items are taken into account
I'm just getting started with silverlight.
Basically I have a silverlight user control that has various dataGrids and a combobox, their item sources set to the properties of a custom plain c# object.
My problem is that I have a dropdown list that when a user selects an item from the list a new row should appear in one of the grids.
All I'm doing is handling the SelectionChanged event and adding a new item to to a list in my custom object and setting the itemsource for the grid again. This doesnt seem to work; no row is added to the dataGrid
I have no idea how to force my grid to "rebind" to this property.
I've been reading about dependency properties, are these what I need?
Any pointers would be really appreciated.
The list you are binding against should be of the type ObservableCollection. Then the datagrid should display the new item automatically .
The problem is that when you assign the same List to the ItemsSource the DataGrid knows its the same List so it does nothing.
As Henrik points out you should expose an Observable<T> not a List<T> for properties that are to be bound to ItemsSource properties of multi-item controls such as DataGrid, ListBox etc.
In addition your "plain c# objects" should implement the INotifyPropertyChanged interface if you want changes made by code to these properties to automatically appear in the UI.
What you probably want to do is update the binding source - which is relatively easily done.
private void ComboBox_SelectionChanged(object sender, RoutedEventArgs e)
{
this.dataGrid.GetBindingExpression(DataGrid.ItemsSource).UpdateSource();
}
This is a tad hack-y but will do what you need it to do. Implementing INotifyPropertyChanged is another great suggestion.
Silverlight show have some great info on INotifyPropertyChanged here
I have a silverlight ListBox that has it's ItemsSource set. From the C# code behind I want to loop through each ListBox item and change the value of the text and access controls that are in the ListBox ItemTemplate. How would I do that?
ListBox controls in silverlight are bound to an ienumerable type, so that if any value in the ListBox changes, the underlying data is changed and vice versa depending on what type of binding you require. To effectively iterate the items you'll want to iterate through the enumerable object you've bound to.
You can get to the collection by accessing the ListBox.ItemsSource property and change the text of appropriate items, perform LINQqueries etc. If you have bound the controls correctly, saving the collection should update the list.
Hope this helps!
I have two ViewModels that present the same Model to different Views. One presents the model as an item in a ListBox, the other presents it as a tab in a TabControl. The TabControl is to display tabs for the items that are selected in the ListBox, so that the tabs come and go as the selection changes.
I can easily synchronise the two controls by adding an IsSelected property to the Model and binding the ViewModels to it (a bit like this), but this will clutter the Model with presentation details that don't really belong there.
It seems like I need something between the Model and ViewModels to hold this extra state. Are there any patterns or examples of a good way to do this?
Use a ViewModel.
You've got a View that contains the two controls. Have a view model that will contain a list of ViewModels for the ListBox control to bind to. Also within this view model bind the listbox selection to a second list of viewmodels that the TabControl then also binds to.
That way your listbox drives what the tab control shows without this information entering the model which should stay oblivious to the existence of the view.
TabControl is ItemsControl, so you shouldn't be shy to bind its ItemsSource to ListBox.SelectedITems.
Obviously ViewModel for List should have a property that would produce ViewModel for Tabs:
public TabViewModel ItemTabModel { get { ... } }
And because TabControl is a bit funny, you'd need to add ItemContainerStyle to populate Content for TabControlItem, because the normal ItemTemplate for TableControl only affects headers for tabs.