Question

I am developing a UserControl, call it CoolControl, that is meant to act somewhat like a window, with a few special features. So far, it can be resized and dragged all around the screen. If I add multiple CoolControl objects to my application window using XAML, the last one that was declared is always in front. This is fine, but I want to make it so that if I click on one of my CoolControl objects during run-time, that control will put itself in front of all the other controls.

I’ve tried using Canvas.SetZIndex, but unless I’m simply unable to come up with a clever enough solution, I don’t see how that can help me. Because once I set one control’s Z-Index to 9999, over time every other control I click will have the same value of 9999. And then, once again, the control declared last ends up in front.

If you were given the task of writing a BringToFront() method for someone’s UserControl, how would you do it in the simplest way possible? I’d prefer a better solution than getting the parent window, looping through all the controls, finding the maximum Z-Index, and then setting the Z-Index of the CoolControl accordingly, if THAT is even a valid solution.

Answer 1

I’m not familiar with the Canvas.SetZIndex method. It looks like some sort of attached property or behaviour.

If you can provide the logic to set the z-index, I’ve outlined a way to keep track of the instances and manage the z-indexes, keeping them in the order in which they have been selected/created.

public class CoolControl : UserControl
{

    public CoolControl()
    {
        InitializeComponent();
        Instances.Add(this);
    }

    static IList<CoolControl> Instances = new List<CoolControl>();

    void SelectThisInstance()
    {
        foreach(var instance in Instances)
        {
            // decrement z-index instance
        }

        // set z-index of this instance to show at top
    }
}