LayoutDocument Is No Longer Displayed

[ColdCodeHah]

LayoutDocument form = new LayoutDocument
            {
                Title =titleIndex++.ToString(),
            };
            LayoutDocumentPane.Children.Add(form);
            form.IsActive = true;   

The code adds pane, And drag leave the pane, And drag enter the pane, And close the pane, The result is run the code LayoutDocument Is No Longer Displayed.

[ColdCodeHah]

The LayoutDocument is there,But does not exist in the visual tree.

[isharrrry]

I also encountered it. After dragging the document out, drag it back and open another document (without displaying the new document) 4.72.1 Not MVVM mode

在源码中这样复现：

1. Add code : LayoutDocumentPane;//
2. Run TestApp and close document 2

3. Drag document 1
4. Drag back document 1

5. click document 1 add documents button can not open another document