Why is this XAML getting the error: Items collection must be empty before using ItemsSource

Question

Can anyone conjure from this code why the ItemsSource line would be getting a

Items collection must be empty before using

Answer 1

You are trying to set the ItemsSource of the ItemsControl but you already have children. Which of those two should apply? The Button you put inside the ItemsControl or the collection you are handing into it as ItemsSource? The error message is perfectly reasonable.

You would have to either remove the button from the ItemsControl or remove the ItemsSource attribute. You can't insert items and set ItemsSource at the same time.

Answer 2

Have you looked at this question? It seems like the answer to your problem.

"Items collection must be empty before using ItemsSource."

Answer 3

Your ItemsControl has a Button in it. Since there's already an item in the ItemsControl, it's not letting you set its ItemsSource property.

Move the Button declaration down under the </ItemsControl> closing tag.