Why ActualWidth and ActualHeight start from 0,0?

I want to add WPF Path to InkCanvas and use selection to select WPF Path. So, I use this code.

System.Windows.Shapes.Path path = drawCanvas.Children[i] as System.Windows.Shapes.Path;    
drawCanvas.Children.RemoveAt(i);
inkCanvas.Children.Add(path);

This is the output. I have to select WPF Path from 0,0 because Actualwidth and ActualHeight start from 0,0.

How do I select absolute WPF Path?

Thanks

Edit:

Now, I can select it absolutely by using this code.

System.Windows.Shapes.Path path = drawCanvas.Children[i] as System.Windows.Shapes.Path;
drawCanvas.Children.RemoveAt(i);
path.Mar开发者_如何学运维gin = new Thickness(-getMinX(path), -getMinY(path), 0, 0);
containPath.Children.Add(path);
containPath.Width = getMaxX(path) - getMinX(path);
containPath.Height = getMaxY(path) - getMinY(path);
containPath.Margin = new Thickness(getMinX(path), getMinY(path), 0, 0);
inkCanvas.Children.Add(containPath);

You can use the UIElement.UpdateLayout Method on the InkCanvas to update the FrameworkElement.ActualWidth Property and ActualHeight. See the ActualWidth link for background information on why this is needed.

Edit:

I misunderstood the question. It wasn't that ActualWidth and ActualHeight were zero but that their values were relative to (0, 0) on the InkCanvas. A pretty good solution to the problem is to wrap the Path in a Canvas and position it using Margin like this:

<Canvas Width="50" Height="50" Margin="200,200,0,0">
    <Line
        X1="0" Y1="0"
        X2="50" Y2="50"
        Stroke="Black"
        StrokeThickness="4" />
</Canvas>

which behaves like:

The disadvantage of this approach is the user has to lasso the Canvas which is a rectangle, not an arbitrary shape. Nevertheless, it's a lot better than having to lasso the object and the origin.

For elements that can only be defined via control points (eg Line, Path etc as against Rectangle, Ellipse etc) when you add it to an items control (which I assume the InkCanvas is since it supports selection), first a canvas is added to the panel at 0,0. The width and the Height of the canvas are determined from the maximum X and Y coordinates of the control points. After this the element is added as a child of this canvas.

You will also see that whenever you see this kind of behaviors with an element, the element wont support Layout Properties like Horizontal/Vertical alignment etc.

The only way I see around this is to find the ActualWidth and ActualHeight manually from the coordinates in the path.

Edit: This is from personal experience and not from any documentation.