this.mediaCenter.ItemManager.Root.SetProgressBar += (val) =>
        {
             this.Invoke((Action)(() =>
            {
                this.progressBarControl1.Position = val;
            }));
        };

private ItemContainerRoot _myRoot;
        public ItemContainerRoot Root
        {
            get { return this._myRoot; }
        }

this._myRoot = context.GetTable<Item>().Single(a => a.Id == 0) as ItemContainerRoot;

class ItemManager : INotifyPropertyChanged
{
    private ItemContainerRoot _myRoot;
    public ItemContainerRoot Root
    {
        get { return _myRoot; }

        set
        {
            _myRoot = value;
            OnPropertyChanged("Root");
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

    protected virtual void OnPropertyChanged(string propertyName)
    {
        PropertyChangedEventHandler handler = PropertyChanged;
        if (handler != null)
        {
            handler(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

ItemManager.PropertyChanged += (o, args) =>
{
     if (args.PropertyName == "Root" && ItemManager.Root != null)
     {
          ItemManager.Root.SetProgressBar += (val) =>
          {
               this.Invoke((Action)(() =>
               {
                    this.progressBarControl1.Position = val;
               }));
          };
     }
};

private Action _myRootDisconnect = null;
private object _myRootGate = new object();
private ItemContainerRoot _myRoot;
public ItemContainerRoot Root
{
    get { return _myRoot; }
    set
    {
        lock (_myRootGate)
        {
            Action<int> setProgressBar = val =>
            {
                this.Invoke((Action)(() =>
                {
                    this.progressBarControl1.Position = val;
                }));
            };

            if (_myRootDisconnect != null)
            {
                _myRootDisconnect();
                _myRootDisconnect = null;
            }

            _myRoot = value;
            _myRoot.SetProgressBar += setProgressBar;

            _myRootDisconnect = () =>
            {
                _myRoot.SetProgressBar -= setProgressBar;
            };
        }
    }
}