>>>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