CODEWITHSUNDEEP
.netwpfdata-bindingobservablecollection
stiank81
stiank81

Reputation: 25686

Binding WPF Canvas Children to an ObservableCollection

In my WPF application I have a Canvas in which I do some drawing. Earlier I handled the drawing in the code behind, but now I've factored everything out to a ViewModel. This gives me some challenges..

I have a few InkPresenter objects holding Strokes. Earier I added them as children to the Canvas in the code behind - like this: 

// Build an InkPresenter: 
var someInkPresenter = BuildInkPresenter(..); 
//_myCanvas is the <Canvas> I want to display it in: 
_myCanvas.Children.Add(someInkPresenter);

Now - not building the InkPresenter in the code-behind of the XAML that holds _myCanvas I need to do this differently. What I'd like to do is to create an InkPresenter and add it to a collection: 

public ObservableCollection<InkPresenter> Drawings;

My problem now is how to bind the Canvas to this ObservableCollection - and have the InkPresenters displayed when added to the collection. Can I achieve this using Data Bindings somehow?

Upvotes: 16

Views: 20824

Answers (2)

Kenneth_hj
Kenneth_hj

Reputation: 495

The solution Anvaka suggested is great, but as John Bowen pointed out you need to know a bit more, if you would like to actually bind your items to the Canvas attached properties.

Here's an example on how to bind to Canvas.Left and Canvas.Top:

<ItemsControl ItemsSource="{Binding YourCollection}">
    <ItemsControl.ItemsPanel>
        <ItemsPanelTemplate>
            <Canvas />
        </ItemsPanelTemplate>
    </ItemsControl.ItemsPanel>
    <ItemsControl.ItemContainerStyle>
        <Style TargetType="ContentPresenter">
            <Setter Property="Canvas.Left" Value="{Binding YourModelLeft}" />
            <Setter Property="Canvas.Top" Value="{Binding YourModelTop}" />
        </Style>
    </ItemsControl.ItemContainerStyle>
</ItemsControl>

Btw, I found the solution on this question, after I tried Anvaka's suggestion, where the binding didn't work.

Hopefully this helps others, looking for the same answer.

Upvotes: 21

Anvaka
Anvaka

Reputation: 15823

I think you can do this with ItemsControl + ItemsPanelTemplate. Like this:

<ItemsControl ItemsSource="{Binding YourCollection}">
    <ItemsControl.ItemsPanel>
        <ItemsPanelTemplate>
            <Canvas />
        </ItemsPanelTemplate>
    </ItemsControl.ItemsPanel>
</ItemsControl>

To read more about this approach refer to Dr.WPF: ItemsControl: A to Z (P is for Panel)

Upvotes: 23

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