Question

I have a

 BindingList<T>

which is bound to a datagridview. One property in my class takes long to calculate, so I threaded the action. After the calculation I raise the OnPropertyChanged() event to notify the grid that the value is ready.

At least, that’s the theory. But since the OnPropertyChanged Method is called from a differend thread I get some weired exceptions in the OnRowPrePaint method of the grid.

Can anybody tell me how I fore the OnPropertyChanged event to be excecuted in the main thread? I can not use Form.Invoke, since the class MyClass is not aware that it runs in a Winforms application.

public class MyClass : INotifyPropertyChanged
{
    public int FastMember {get;set;}

    private int? slowMember;
    public SlowMember
    {
        get
        {
            if (slowMember.HasValue)
               return slowMember.Value;
            else
            {
               Thread t = new Thread(getSlowMember);
               t.Start();
               return -1;
            }

        }
    }

   private void getSlowMember()
   {
       Thread.Sleep(1000);
       slowMember = 5;
       OnPropertyChanged("SlowMember");
   }

   public event PropertyChangedEventHandler PropertyChanged;
   private void OnPropertyChanged(string propertyName)
   {
        PropertyChangingEventHandler eh = PropertyChanging;
        if (eh != null)
        {
            eh(this, e);
        }
   }

}

Answer 1

By design, a control can only be updated by the thread it was created in. This is why you are getting exceptions.

Consider using a BackgroundWorker and only update the member after the long lasting operation has completed by subscribing an eventhandler to RunWorkerCompleted.