>>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.