ObservableCollection<Double[]> and XAML - multidimensional-array

Question

I have a class that inherits ObservableCollection< Double[] > (let's call it "TestClass"). I.e. collection of double arrays. Can I use this kind of collection in XAML. I'm trying to add items but it looks like I cannot add double arrays as items. Is this even possible?
Something like this:
<TestClass>
<x:Array Type="sys:Double">
<!-- What comes here...? -->
</x:Array>
</TestClass>
Actually, I would rather like to use ObservableCollection< Double[,] > but I think it's impossible - two-dimensional array I mean.
Help me out here... :)

Answer 1

First, you need a ViewModel. The ViewModel will be your container class where we insert custom double-arrays or fetch them from the database. If it's not just a lookup, you will need to implement INotifyPropertyChanged (but that's a different topic):
namespace MyCompany.Common.ViewModels
{
using System.ComponentModel;
using System.Runtime.CompilerServices;
public class PointsArrayVM
{
private double[] _points;
public double[] Points
{
get
{
return _points;
}
set
{
_points = value;
}
}
}
}
In this example, I'll add two custom records of double[] (firstArray & secondArray). I then assign the collection to a CollectionViewSource, and (just to illustrate) I assign more records from the database to a second CollectionViewSource with the exposed MainViewModel property, List<PointsArrayVM> DatabasePoints. If it's not just a lookup, you will need an ObservableCollection instead of a List. In your XAML, under Window.Resources, add the following:
<x:Array x:Key="firstArray" Type="sys:Double"
xmlns:sys="clr-namespace:System;assembly=mscorlib">
<sys:Double>1.1</sys:Double>
<sys:Double>1.2</sys:Double>
<sys:Double>1.3</sys:Double>
</x:Array>
<x:Array x:Key="secondArray" Type="sys:Double"
xmlns:sys="clr-namespace:System;assembly=mscorlib">
<sys:Double>2.1</sys:Double>
<sys:Double>2.2</sys:Double>
<sys:Double>2.3</sys:Double>
</x:Array>
<x:Array x:Key="pointsArray" Type="{x:Type viewmodels:PointsArrayVM}"
xmlns:viewmodels="clr-namespace:MyCompany.Common.ViewModels;assembly=Common">
<viewmodels:PointsArrayVM Points="{StaticResource firstArray}"/>
<viewmodels:PointsArrayVM Points="{StaticResource secondArray}"/>
</x:Array>
<CollectionViewSource x:Key="customPointsCollectionViewSource" Source="{StaticResource pointsArray}"/>
<CollectionViewSource x:Key="databasePointsCollectionViewSource" Source="{Binding DatabasePoints}"/>
Now that we have our CollectionViewSources, we can add them to a CompositeCollection with CollectionContainers. In this example I'm using Points[0] as the display text, and Points1 as the selected value:
<ComboBox Text="{Binding PointsFilter}" VerticalAlignment="Top"
SelectedValuePath="Points[0]" DisplayMemberPath="Points[1]">
<ComboBox.ItemsSource>
<CompositeCollection>
<CollectionContainer Collection="{Binding Source={StaticResource customPointsCollectionViewSource}}"/>
<CollectionContainer Collection="{Binding Source={StaticResource databasePointsCollectionViewSource}}"/>
</CompositeCollection>
</ComboBox.ItemsSource>
</ComboBox>
I hope this helps! For some very informative XAML tips, have a look at this site.
Regarding your second question
Yes, WPF seems to have a problem with assigning a control path to a specific point in a multi-dim array. You can however work around this by also having a Points2DArray ViewModel that contains an array of PointsArrayVM objects:
namespace MyCompany.Common.ViewModels
{
using System.ComponentModel;
using System.Runtime.CompilerServices;
public class Points2DArrayVM
{
private PointsArrayVM[] _pointsArrays;
public PointsArrayVM[] PointsArrays
{
get
{
return _pointsArrays;
}
set
{
_pointsArrays = value;
}
}
}
}
So in your XAML, you can now put the collections of one ViewModel into the other container ViewModel:
<x:Array x:Key="pointsArray1" Type="{x:Type viewmodels:PointsArrayVM}"
xmlns:viewmodels="clr-namespace:MyCompany.Common.ViewModels;assembly=Common">
<viewmodels:PointsArrayVM Points="{StaticResource firstArray}"/>
<viewmodels:PointsArrayVM Points="{StaticResource secondArray}"/>
</x:Array>
<x:Array x:Key="pointsArray2" Type="{x:Type viewmodels:PointsArrayVM}"
xmlns:viewmodels="clr-namespace:MyCompany.Common.ViewModels;assembly=Common">
<viewmodels:PointsArrayVM Points="{StaticResource firstArray}"/>
<viewmodels:PointsArrayVM Points="{StaticResource secondArray}"/>
</x:Array>
<x:Array x:Key="points2DArray" Type="{x:Type viewmodels:Points2DArrayVM}"
xmlns:viewmodels="clr-namespace:MyCompany.Common.ViewModels;assembly=Common">
<viewmodels:Points2DArrayVM PointsArrays="{StaticResource pointsArray1}"/>
<viewmodels:Points2DArrayVM PointsArrays="{StaticResource pointsArray2}"/>
</x:Array>
<CollectionViewSource x:Key="customPointsCollectionViewSource" Source="{StaticResource points2DArray}"/>
Then in your ComboBox, it would be something like:
<ComboBox Text="{Binding PointsFilter}" VerticalAlignment="Top"
SelectedValuePath="PointsArrays[0].Points[0]" DisplayMemberPath="PointsArrays[0].Points[1]">
<ComboBox.ItemsSource>
<CompositeCollection>
<CollectionContainer Collection="{Binding Source={StaticResource customPointsCollectionViewSource}}"/>
</CompositeCollection>
</ComboBox.ItemsSource>
</ComboBox>