Wpf ItemsControl with margin coordinates [duplicate] - wpf

Question

I want to add a set of rectangles to the main window of my mvvm application. In my viewModel I've got a collection of objects which I convert to System.Windows.Shapes.Rectangle classes with a converter (code below):
ViewModel:
RecognizedValueViewModel
{
public ObservableCollection<BarcodeElement> BarcodeElements
{
get { return _BarcodeElements; }
set { _BarcodeElements = value; }
}
public RecognizedValueViewModel()
{
BarcodeElements = InitializeBarcodeElements();
}
}
Converter:
public BarcodeElementToRectangleConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
Rectangle barcodeRectangle = GetRectangleFromBarcodeElement(value as BarcodeElement);
return barcodeRectangle;
}
}
The rectangles should be shown in a canvas in my MainWindow:
<Canvas x:Name="Canvas_Image_Main">
<!-- Show rectangles here -->
</Canvas>
I would add Rectangles to canvas in code but I don't now how many rectangles are there at runtime. Is there a way how I can achieve this? Tank you.

Answer 1

In a proper MVVM approach you would have a view model with an abstract representation of a list of rectangles, e.g. like this:
public class RectItem
{
public double X { get; set; }
public double Y { get; set; }
public double Width { get; set; }
public double Height { get; set; }
}
public class ViewModel
{
public ObservableCollection<RectItem> RectItems { get; set; }
}
Then you would have a view that uses an ItemsControl to visualize a collection of such Rect items. The ItemsControl would have a Canvas as its ItemsPanel and an appropriate ItemContainerStyle and ItemTemplate which each bind to the appropriate view model properties. It might look like this:
<ItemsControl ItemsSource="{Binding RectItems}">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<Canvas/>
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemContainerStyle>
<Style TargetType="ContentPresenter">
<Setter Property="Canvas.Left" Value="{Binding X}"/>
<Setter Property="Canvas.Top" Value="{Binding Y}"/>
</Style>
</ItemsControl.ItemContainerStyle>
<ItemsControl.ItemTemplate>
<DataTemplate>
<Rectangle Width="{Binding Width}" Height="{Binding Height}" Fill="Black"/>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
An alternative without Bindings in Style Setters (which don't work in UWP) might look like this:
<ItemsControl ItemsSource="{Binding RectItems}">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<Canvas/>
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate>
<Rectangle Width="{Binding Width}" Height="{Binding Height}" Fill="Black">
<Rectangle.RenderTransform>
<TranslateTransform X="{Binding X}" Y="{Binding Y}"/>
</Rectangle.RenderTransform>
</Rectangle>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>

Answer 2

You can bind the collection of rectangles to an ItemControl and set its height, width and margin:
<ItemsControl ItemsSource="{Binding Path=RectangleCollection,Mode=TwoWay}">
<ItemsControl.ItemTemplate>
<DataTemplate >
<Canvas>
<Rectangle Stroke="Black" Heigth={some converter} Width={some converter} Margin={Some Converter}>
</Canvas>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemControl>
Just an idea to get you started...