How can I get the elements of a canvas?

Question

I have this:

<Canvas x:Name="can" HorizontalAlignment="Left" Height="502" Margin="436,0,0,0" VerticalAlignment="Top" Width="336" OpacityMask="#FFC52D2D">
    <Canvas.Background>
        <SolidColorBrush Color="{DynamicResource {x:Static SystemColors.ActiveCaptionColorKey}}"/>
    </Canvas.Background>
    <Button x:Name="btn_twoThreads" Content="Two Threads" Height="32" Canvas.Left="195" Canvas.Top="460" Width="131" Click="btn_twoThreads_Click"/>
    <Button x:Name="btn_oneThread" Content="One Thread" Height="32" Canvas.Left="10" Canvas.Top="460" Width="131" Click="btn_oneThread_Click"/>
    <Rectangle Fill="#FFF4F4F5" Height="55" Canvas.Left="10" Stroke="Black" Canvas.Top="388" Width="316"/>
</Canvas>

As you can see there are some objects on this canvas in the XAML Code. I need to get the the Rectangle object's details:

Rectangle r; 

r = can.Children[2] as Rectangle; //I know this probably doesn't retrieve the rectangle object, but hopefully you can see what I am trying to achieve.

if (r != null)
{
    MessageBox.Show("It's a rectangle");
}

I know I could probably just access the Rectangle object by just giving it a variable name in the XAML, but the canvas object is being drawn to in various classes, and I don't want to pass the rectangle to every class if it is already contained within the canvas.

`can.Children[2]` will get you rectangle. Are you getting any errors or what? — Rohit Vats, Oct 12 '13 at 19:11
If I'm understanding you correctly, you could always write this as a custom user control and expose public getters for the buttons/rectangles as appropriate. Especially if (from what it sounds like) you are using similar/identical canvas markup in several places. — Chris Sinclair, Oct 12 '13 at 19:12
If you know what type they are, you can do something like this: http://stackoverflow.com/questions/974598/find-all-controls-in-wpf-window-by-type — Millie Smith, Oct 12 '13 at 21:10

Jeroen van Langen · Accepted Answer · 2013-10-14T07:32:01.287

10

You could try this:

// to show that you'll get an enumerable of rectangles.
IEnumerable<Rectangle> rectangles = can.Children.OfType<Rectangle>();

foreach(var rect in rectangles)
{
    // do something with the rectangle
}

Trace.WriteLine("Found " + rectangles.Count() + " rectangles");

The OfType<>() is very useful because it checks the type and only yields an item if it is the right type. (it's casted already)

edited Oct 14 '13 at 07:32

answered Oct 12 '13 at 21:40

Jeroen van Langen

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How can I get the elements of a canvas?

1 Answers1