Question

I currently have a user control that contains items that have a certain X, Y coordinate and there are limits to what those points must be within. In this case those positions are 0 > X > 40 and 0 > Y > 80 (40×80). The control I am hosting those items in is dynamic but has a certain aspect ratio based on window size. I need to translate those X & Y coordinates into relative locations within the user control. Any help is greatly apprecaited! Thanks in advance! If it matters/helps, I’m using Silverlight.

Answer 1

you can use GeneralTransform to determine a UIElement’s position relative to a container. Here’s a snippet:

    /// <summary>
    /// Gets the position of the specified element's top left corner, relative to the specified container.
    /// </summary>
    /// <param name="element"></param>
    /// <param name="container"></param>
    public static Point GetPosition(UIElement element, UIElement container)
    {
        if (element == null)
            throw new ArgumentNullException("element");
        if (container == null)
            throw new ArgumentNullException("container");
        var gt = element.TransformToVisual(container);
        var position = gt.Transform(new Point(0, 0));
        return position;
    }

Cheers, Alex

[EDIT] In fact, checking “container” for null is unnecessary – TransformToVisual will also accept null as parameter.
Another issue: TransformToVisual will throw an ArgumentException e.g. when “element” is not visible, is currently not in the visual tree etc. etc.
Unfortunately, I could not find a way to determine whether TransformToVisual will throw that exception before actually calling it on “element”. So I simply wrapped calls to TransformToVisual in a try-catch block and swallowed the ArgumentException, because it is quite useless anyway IMHO.