Wpf Bring to Front

Question

I have a ItemsControl which uses a Canvas as as as the ItemsPanel. The itemsTemplate hosts a Custom Control. When the control is clicked I would like it to "move to the front". I know I can do this with the ZIndex in my control like so:

 private void MyControl_PreviewMouseDown(object sender, MouseButtonEventArgs e)
{
    if(((FrameworkElement)sender).TemplatedParent==null) return;
    ContentPresenter presenter = (ContentPresenter)((FrameworkElement) sender).TemplatedParent;

    int currentValue = Panel.GetZIndex(presenter);
    Console.WriteLine(currentValue);
    Panel.SetZIndex(presenter, 99);
}

This works and sets the ZIndex just fine. But when I click on a different control in the ItemsControl it will get the exact same ZIndex so it will not "move in front" of the other control.

Basically I just want the same behavior as windows exhibit.

I've tried setting the ZIndex back to 0 in the PreviewMouseUp event, and that ensures that the clicked control is always at the top, but then since all other controls have the same ZIndex of 0 then will assume default order based on there position in the list.

An example:

Lets say I have 3 controls all with a ZIndex of 0. (so they use the default list position.)

If I click on control 3, then 2 then 1. I would expect it to have 3 at the top of the ZOrder, then 2 then 1. But since I'm setting the ZIndex to zero on MouseUp it would have the default order of 1,2,3.

Is there an easy way to handle this or do I need to keep track of the order and increment decrement an arbitrary value such as 99 on my own?

Solution

I would do something along these lines:

Upon mouse down set the Z-index on the selected control to a very high number. Have a static int Zindex initialized to 0. Upon mouse up set the Z-index equal to Zindex++

private static int Zindex = 0;

private void MyControl_PreviewMouseDown(object sender, MouseButtonEventArgs e)
{
    if(((FrameworkElement)sender).TemplatedParent==null) return;
    ContentPresenter presenter = (ContentPresenter)((FrameworkElement) sender).TemplatedParent;

    int currentValue = Panel.GetZIndex(presenter);
    Console.WriteLine(currentValue);
    Panel.SetZIndex(presenter, Int32.MaxValue);
}

private void MyControl_PreviewMouseUp(object sender, MouseButtonEventArgs e)
{
    if(((FrameworkElement)sender).TemplatedParent==null) return;
    ContentPresenter presenter = (ContentPresenter)((FrameworkElement) sender).TemplatedParent;

    int currentValue = Panel.GetZIndex(presenter);
    Console.WriteLine(currentValue);
    Panel.SetZIndex(presenter, Zindex++);
}

If your program should be running for a long time you could have some upper limit on Zorder, so if reached you could find the smallest z-index in use and substract this from the z-index on all controls and the Zindex counter.