dotnet/wpf · error

SR.DocumentGridVisualTreeContainsNonUIElement

Error message

SR.DocumentGridVisualTreeContainsNonUIElement

What it means

InvalidOperationException from DocumentGrid.ArrangeOverride: a visual child being arranged is not a UIElement, meaning the internal visual tree was tampered with. Arrangement requires UIElement children to apply offsets, so the guard throws.

Solutions

1. Do not insert arbitrary Visuals into the DocumentGrid child collection
2. Use the public document/paging APIs to alter content

When it happens

Trigger: Thrown at src/Microsoft.DotNet.Wpf/src/PresentationFramework/MS/Internal/documents/DocumentGrid.cs:1217 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/a0a44b82865a9bfd. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationFramework/MS/Internal/documents/DocumentGrid.cs:1217

                    //Arrange the page if necessary
                    UIElement uiPage = _childrenCollection[visualChild] as UIElement;
                    if (uiPage != null)
                    {
                        Point pageOffset;
                        //Move the page to the right place based on the FlowDirection of the content.
                        if (_pageCache.IsContentRightToLeft)
                        {
                            pageOffset = new Point(Math.Max(ViewportWidth, ExtentWidth) - (xOffset + pageSize.Width), yOffset);
                        }
                        else
                        {
                            pageOffset = new Point(xOffset, yOffset);
                        }
                        uiPage.Arrange(new Rect(pageOffset, pageSize));
                    }
                    else
                    {
                        throw new InvalidOperationException(SR.DocumentGridVisualTreeContainsNonUIElement);
                    }

                    //Increment our horizontal offset to point to where the next page should go.
                    xOffset += (pageSize.Width + HorizontalPageSpacing);

                    //Move to the next page.
                    visualChild++;
                }
            }

            // As we scroll we need to keep the AdornerLayer up-to-date.
            // This ensures that annotation components scroll with the content.
            AdornerLayer layer = AdornerLayer.GetAdornerLayer(this);
            if (layer != null && layer.GetAdorners(this) != null)
                layer.Update(this);

            return arrangeSize;
        }

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