[dansiegel]

Description of Change

On Windows, changing a toolbar item's image can briefly leave the new image source without a parent. MAUI then falls back to application services, where DryIoc can auto-construct an unusable WinUI Window. Image conversion throws when MAUI requests its display density.

Register an optional null native window at application scope on Windows. MAUI's window contexts continue to supply their actual windows, and TryAddSingleton preserves explicit registrations.

Validation:

• Two Windows service tests in the existing MAUI DryIoc test project pass on MAUI 10.0.10. They cover the optional lookup through the real Prism builder/container and preservation of an explicit registration. The lookup test fails without the fix because DryIoc constructs a native window.
• All 275 existing portable MAUI DryIoc tests pass on .NET 10.
• Separate local native runtime checks passed on MAUI 10.0.10 and 10.0.20, using both normal Prism startup and plain MAUI window creation. They verified rendered toolbar images through repeated resource-dictionary swaps, direct source replacement, clearing, and restoration. These rendering checks are not part of the committed headless test suite.

Bugs Fixed

• Fixes [BUG] Windows - NullReferenceException when ToolbarItem.IconImageSource changes after UsePrism is registered #3448

API Changes

None.

Behavioral Changes

None beyond the bug fix.

PR Checklist

• Has tests (if omitted, state reason in description)
• Rebased on top of master at time of PR
• Changes adhere to coding standard

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-15T20:16:23.359643Z	9f16fd1	PR opened

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