>>>>>Well... I found two errors to start with.
>>>>>
>>>>>

     private void NotifyPropertyChanged(String info)
>>>>>        {
>>>>>        if (PropertyChanged != null)
>>>>>          {
>>>>>          PropertyChanged(this, new PropertyChangedEventArgs(info));
>>>>>          //CollectionChanged was null commented it off
>>>>>          //CollectionChanged(this, new CollectionChangeEventArgs(CollectionChangeAction.Refresh, this.HoleList));
>>>>>          }
>>>>>        }

>>>>>
>>>>>Second was that repaint screen was not getting called. You are binding to CurrentHolePattern so:
>>>>>
>>>>>

CurrentHolePattern.PropertyChanged += new PropertyChangedEventHandler(CurrentHolePattern_PropertyChanged);

>>>>>
>>>>>This looks like it works:
>>>>>
>>>>>

    public Window1()
>>>>>      {
>>>>>
>>>>>      HolePatterns = new ObservableCollection<HolePattern>();
>>>>>      HolePatterns.CollectionChanged += new NotifyCollectionChangedEventHandler(HolePatterns_CollectionChanged);
>>>>>
>>>>>      CurrentHolePattern = new HolePattern();
>>>>>      CurrentHolePattern.PatternName = "Test Pattern Name";
>>>>>
>>>>>      //-- Set some default values for the UI
>>>>>      CurrentHolePattern.BoltCirDia = 12.0;
>>>>>      CurrentHolePattern.HoleCount = 6;
>>>>>      CurrentHolePattern.StartAngle = 0;
>>>>>
>>>>>      HolePatterns.Add(CurrentHolePattern);
>>>>>
>>>>>      InitializeComponent();
>>>>>      CurrentHolePattern.PropertyChanged += new PropertyChangedEventHandler(CurrentHolePattern_PropertyChanged);
>>>>>
>>>>>      SketchX0 = canvas1.Width / 2;
>>>>>      SketchY0 = canvas1.Height / 2;
>>>>>      SketchBoltCirRad = canvas1.Width / 2 * .7;
>>>>>
>>>>>      CoordinateGrid.ItemsSource = CurrentHolePattern.HoleList;
>>>>>
>>>>>      RedrawScreen();
>>>>>      }
>>>>>
>>>>>    void CurrentHolePattern_PropertyChanged(object sender, PropertyChangedEventArgs e)
>>>>>      {
>>>>>      RedrawScreen();
>>>>>      //RepaintScreen();  Repaint doesn't add new holes.
>>>>>      }
>>>>>

>>>>
>>>>Dang. Just read this. I pulled in Matt's code last night and had made *exactly* the same changes that you pointed out. But then it would not run - I got a XMLParseException:
>>>>Cannot create instance of 'Window1' defined in assembly 'WpfApplication1, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'. Exception has been thrown by the target of an invocation. Error in markup file 'Window1.xaml' Line 1 Position 9.
>>>>
>>>>Didn't have time to look at it any more and don't now either but it's still giving that error unless the RedrawScreen() line is commented out in the event handler.
>>>>???
>>>>Regards,
>>>>Viv
>>>
>>>Did you put the
>>>
>>>CurrentHolePattern.PropertyChanged += new PropertyChangedEventHandler(CurrentHolePattern_PropertyChanged);
>>>
>>>before the
>>>
>>>InitializeComponent();
>>>
>>>by any chance? That will throw that error.
>>
>>Very possibly. But, as I just mentioned to Matt, without thinking I pasted his newer version over the top of the one with my changes so now I'll never know for sure. IAC I'll know what to check if I make the same mistake in the future!
>>Thanks,
>>Viv
>
>The only reason it came to mind is that I made that mistake myself.<g>

Did you actually deduce the cause of the error from the exception message? To me it provided no clue at all!