Joan Venge Joan Venge - 1 month ago 18
C# Question

What's the best way to update an ObservableCollection from another thread?

I am using the

BackgroundWorker
to update an
ObservableCollection
but it gives this error:


"This type of
CollectionView
does
not support changes to its
SourceCollection
from a thread
different from the Dispatcher thread."


What's the best and most elegant way to solve this, with the least amount of work. I don't want to write low level lock-based multi-threading code.

I have seen some solutions online but they are several years old, so not sure what the latest consensus is for the solution of this problem.

Answer

If MVVM

public class MainWindowViewModel : ViewModel {

    private ICommand loadcommand;
    public ICommand LoadCommand { get { return loadcommand ?? (loadcommand = new RelayCommand(param => Load())); } }

    private ObservableCollection<ViewModel> items;
    public ObservableCollection<ViewModel> Items {
        get {
            if (items == null) {
                items = new ObservableCollection<ViewModel>();
            }
            return items;
        }
    }

    public void Load() {
        BackgroundWorker bgworker = new BackgroundWorker();
        bgworker.WorkerReportsProgress = true;
        bgworker.DoWork += (s, e) => {
            for(int i=0; i<10; i++) {
                System.Threading.Thread.Sleep(1000);
                bgworker.ReportProgress(i, new List<ViewModel>());
            }
            e.Result = null;
        };
        bgworker.ProgressChanged += (s, e) => {
            List<ViewModel> partialresult = (List<ViewModel>)e.UserState;
            partialresult.ForEach(i => {
                Items.Add(i);
            });
        };
        bgworker.RunWorkerCompleted += (s, e) => {
            //do anything here
        };
        bgworker.RunWorkerAsync();
    }
}