What is a simple way to add Scrollbars to a ListBox?

I would suggest using a ScrollViewer instead of relying on VerticalScrollBarVisibility.

See this example...

In XAML, the ListBox control automatically provides scrollbars when its content exceeds the available space. However, if you want to ensure that the vertical scrollbar is always visible, you can set the ScrollViewer.VerticalScrollBarVisibility property to "Visible," as you've already done in your example.

Here's a simple way to add scrollbars to a ListBox:

Setting VerticalScrollBarVisibility to "Auto" will show the scrollbar only when needed, while "Visible" will always show it. You can also add items to the ListBox to see the scrollbars in action.

To check that the scrollbar in your ListBox scrolls its contents, you need to make sure the ListBox has a constrained height or is inside a container with limited size

    
        
            
                
                Item 1
                Item 2
                Item 3
                Item 4
                Item 5
                Item 6
                Item 7
                Item 8
                Item 9
                Item 10
                Item 11
                Item 12
                Item 13
            
        
    

The ListBox needs to have a constrained height or width. In the example, the Grid container implicitly limits the size of the ListBox based on the Window size. 

• ScrollViewer.VerticalScrollBarVisibility="Auto" ensures the vertical scrollbar appears when needed.
• You can use ScrollViewer.HorizontalScrollBarVisibility="Auto" for a horizontal scrollbar, if required.