Hello,
This big can be reproduced in your demo application:
- Open the GridView examples
- In the available examples, select "Selection and Usability | Row Details"
- Select a rowin the grid view
- In the external Details Presenter, select Visible: nothing is displayed in the bottom. You have to select another row and then come back to show the details.
Also another problem: if the external details is inside a ContentPresenter (collapsed at the beginning), it can't find the gridview.
To test this, replace your Border with a ContentPresenter.