A better way of forcing data bound WPF ListBox to update?
WPF binding a list / collection of items to a ListBox, but UI not refreshing after items updated, Solved.
I'm just stupid. While I'd read a lot about using ObservableCollection<>
instead of List<>
, I just continued to ignore this suggestion and went following other suggestions, to no avail. Got back to my books and reread. It's pretty well explained that ObservableCollection<>
is a must use because List<>
doesn't provide the INotifyCollectionChange
interface needed for the ListBox
to update its display when the items change in the collection.
This is the updated code:
private ObservableCollection<StringWrapper> m_AppLog;
ObservableCollection<StringWrapper> Log { get { return m_AppLog; } }
Pretty simple, and doesn't require anything else (e.g. Refresh()). Because ObservableCollection takes care itself of triggering the change event, I was able to remove the unnecessary call:
// notify bound objects
OnPropertyChanged("Log");
ObservableCollection
doesn't support an update by a thread which didn't create it. Because my list (a visual log to show the recent errors/info messages) can be updated from different threads, I add to adjust my code this way to ensure the update was done with the list's own dispatcher:
public void AddToLog(string message) {
if (Thread.CurrentThread != Dispatcher.Thread) {
// Need for invoke if called from a different thread
Dispatcher.Invoke(
DispatcherPriority.Normal, (ThreadStart)delegate() { AddToLog(message); });
}
else {
// add this line at the top of the log
m_AppLog.Insert(0, new StringWrapper(message));
// ...
Also note that ObservableCollection<>
doesn't support RemoveRange()
contrary to List<>
. This is part of the possible adjustments required when switching from List to ObservableCollection.
I had the same problem yesterday, and it's a complete piece of crap :) ... I'm not setting mine to null anymore though. In my scenario, I am setting it to MyList.ToArray() (after every time I add to the list).
I've seen multiple "oh, you need to use an ObservableList" <-- complete crap.
I've seen multiple "oh, call 'Refresh'" <-- complete crap.
Please forgive my upsettedness, but I also would expect this to work :)
I have a Listbox bound to an object property which is of type List<MyCustomType>()
and I verified that the following code updates the listbox when the List is updated.
void On_MyObjProperty_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
{
MyListBox.Items.Refresh();
}
If you're still facing issues, scan the VS IDE output window (Ctrl+W, O) and see if you can spot any binding errors reported.
I may be having a similar problem to what you are having, but I'm not sure.
I had an ObservableCollection<MyEntity>
and a ListBox
bound to it. But for some strange reason my ListBox
was not being updated when I changed the properties of the MyEntity
objects in the list.
After searching for a while I found the following page and I just had to let you know:
http://www.wblum.org/listbind/net3/index.html
It is a very good description of what you have to do to get a ListBox
to update when the list, or the objects within it, changes. Hoping you will benefit from this.