If your creating a class that implements one of the Change interfaces, yes you have to fully hook them up in that class, and call the correct events when things change.
Once that is done things are pretty automatic.
You might have even been able to achive a greater level of automation if you had created your circles on the canvas with an items control. WPF is really sweet in how it handles things like that. But, I think you should wait till you get the hang of a few more things before you try that. It will require learning a few more new concepts.
John
>Thanks John... You helped me see that I could just look at PropertyChanged to do what I need, and that I need to be looking at the CurrentHolePattern.PropertyChanged, not the HolePatterns = new ObservableCollection
() that I was trying to hook up. I was so focused on looking for a change to the HoleList collection and using some CollectionChanged event.
>
>In the end, I think there will be times when you really need to be watching for a CollectionChanged event to respond to. In my current case, I can get by with knowing that a change in the HoleCount property means that the HoleList collection has been changed (at least it was supposed to be).
>
>For now, I am moving on with Property watching, but one day I'd like to explore a lower-level monitoring of changes in the the actual HoleList colleciton to respond to.
>
>In the end, after 5+ hours of head-banging, this has helped me realized that PropertyChanged event announcement really falls fully on the programmer to make it all work. Even though you throw a INotifyPropertyChanged interface on your class, you still have to write a few support methods, an most importantly, you must be sure to properly announce every property change so the the watchers can respond. I surely expected something a little more automatic than that.
>
>I suppose I will find with CollectionChanged that I must also tell my class when to tell everyone else that the collection has changed. Dang it, why can't it just do that for me?
>
>
>Anyway, back to my program:
>
>I'm still adhering to the different uses that I designed between RedrawScreen() and RepaintScreen: RepaintScreen() is really only required if the HoleCount changes, because I would need to remove some Ellipses from the Canvas or add some more. So, I just clear the Canvas and start all over; whereas RepaintScreen() actually works to re-arrange (move) the Ellipses and Labels that are already there. My conceren was that it would be slow to clear-the-canvas everytime a property changed, but really it's so fast that it doesn't matter. However, I'm sticking with the model I designed just as a learning example for slightly more complex coding. I'm imagining a 10,000 element model and how would you most efficiently program for that. (Not a real case, but fun to think about)!
>
>
>
>So here is my PropertyChanged event:
>>
> void CurrentHolePattern_PropertyChanged(object sender, PropertyChangedEventArgs e)
> {
> if (e.PropertyName == "HoleCount")
> {
> RedrawScreen(); // Clear Canvas and re-build everything!
> }
> else
> {
> RepaintScreen();// Repaint doesn't clear out the Canvas, just updates what's already there.
> }
> }
>
>
>>
>
>
>>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.
>> }
>>
