Question

Update2

I’ve rewritten the entire question, because some things became a lot clearer, the issue now seems to be that I created a list of DependencyProperties on a different thread than where the DependencyProperties will be used :(.

When I do some work on a BackgroundWorker the XAML bindings cause an ArgumentException

Must create DependencySource on same Thread as the DependencyObject.

I’ve got the following setup:

I’ve got a simple class that implements INotifyPropertyChanged which contains a few ints, list’s and Dictionaries.

public class Calculator : INotifyPropertyChanged
{
    //Note that InstanceGroup is a dependency object
    private List<InstanceGroup> instanceGroups = new List<InstanceGroup>();
    public List<InstanceGroup> InstanceGroups
    {
        get { return instanceGroups; }
        set { instanceGroups = value; }
    }

    // snip //

    public void Calculate()
    {
        InstanceGroups = MyNewFilledInstanceGroup;
            if (PropertyChanged != null)
            {
              PropertyChanged(this, new PropertyChangedEventArgs("instanceGroups"));
            }
    }
}

In a UserControl I use a BackgroundWorker to run the Calculate method, because it can take a lot of time:

BackgroundWorker worker = new BackgroundWorker();
worker.DoWork += delegate(object o, DoWorkEventArgs args)
{
    lock (Calculator)
    {       
        Calculator.Calculate();
    }
};
worker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(worker_RunWorkerCompleted);
worker.RunWorkerAsync();

In the XAML file of the UserControl I have multiple bindings to the Calculator, like {Binding Path=Calculator.InstanceGroups, Path=userControlName}.

(The overall goal is to be able to do all the work in the Calculate method on a separate thread so I can show a progress bar or something like that)

Answer 1

The only solution seems to be to not create DependencyProperties ( How to handle ObservableCollection<> result from a parallelized Task in MVVM? ) in a background task, this weird behavior costed me the better part of the day. But at least now I know what the problem was.