WPF边框属性无法正常工作

Question

I am working on an application that is using Drag and Drop functionality. When I drag certain items over other items, I would like to show if they are towards the top, or the bottom of the item by setting the border property of the item they are over dynamically(as oppose to in the xaml).

I have looked into this, and used examples, but none of them are working. Here is the code I have that is called when a drag operation is performed over the Grid Item.

 private void Grid_DragEnter(object sender, DragEventArgs e)
    {
        Grid grid = (Grid)sender;
        grid.Background = Brushes.Cornsilk;

        Border border = new Border();
        border.BorderBrush = Brushes.Black;
        border.BorderThickness = new Thickness(5, 10, 15, 20);
        border.Background = Brushes.Black;
        border.Padding = new Thickness(10);
        border.Child = grid;
    }

The code above is only test code so that I can see the border is showing. Once I can get this, then I will set the top or bottom border at separate times, depending on if they are above or below the center of the grid item.

Answer 1

You're setting the border's child, but the border itself needs to be added to some container in order for it to be visible.

That being said, you might want to look into Adorners . They are designed for exactly this scenario, and don't require changing the visual hierarchy of your UI at runtime.