Automatically update 2 dimensional array based on list content

Question

Suppose I have a simple class named SimplePoint
class SimplePoint
public int x { get; set; }
public int y { get; set; }
Next I create an ObservableCollection of the class and bind it to a WPF DataGrid via XAML.
Each SimplePoint has a distance to each other SimplePoint int the list, resulting in a matrix. The distance from point a to b can be different from the distance from point b to a (ie. different route).Distances should be editable.
I wonder how I can create a class, that can automatically keep track of changes in the ObservableCollection<SimplePoint>. When a new SimplePoint is added, one row and one column should be added to the distances matrix. When a SimpePoint is removed,
the appropriate entries in the matrix should be removed. Later I also wish to store and retrieve all the info to and from an XML via serialization.
So this list:
point1
point2
point3
Would yield a 3x3 matrix of distances.
Searching a lot did not yield results, though I am unsure if I looked for the right thing. I cannot get my head around how to organize this internally. Maybe something like ObservableCollection<ObservableCollection<SimplePoint>>, but then how
to maintain that, and how to bind it to a DataGrid... Any ideas?

Answer 1

Hi mennowo,
>> that can automatically keep track of changes in the ObservableCollection<SimplePoint>. When a new SimplePoint is added, one row and one column should be added to the distances matrix
I would recommend that you can use ObservableCollection<T>.CollectionChanged event:
https://msdn.microsoft.com/en-us/library/ms653375(v=vs.110).aspx
This event will be triggered when items are added, removed, changed, moved, or the entire list is refreshed. In this event, you can easily add item into the distances matrix as you wish.
Here is a simple sample:
public ObservableCollection<SimplePoint> DemoSource { get; set; }
public MainWindow()
InitializeComponent();
DemoSource = new ObservableCollection<SimplePoint>();
DemoSource.CollectionChanged += MyItemsSource_CollectionChanged;
DemoSource.Add(new SimplePoint() { x = 1, y = 1 });
DemoSource.Add(new SimplePoint() { x = 2, y = 2 });
DemoSource.Add(new SimplePoint() { x = 3, y = 3 });
this.DataContext = this;
private void MyItemsSource_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
if (e.NewItems != null)
foreach (SimplePoint item in e.NewItems)
//Add this item into the distances matrix
if (e.OldItems != null)
foreach (SimplePoint item in e.OldItems)
//Do something for old items
We are trying to better understand customer views on social support experience, so your participation in this interview project would be greatly appreciated if you have time. Thanks for helping make community forums a great place.
Click
HERE to participate the survey.