7. Reload and diagnose

Use the final sample entry point for development reload. It selects ReloadHost only when the imported targets define XUI_HOT_RELOAD. Release builds use an ordinary disposable Window and Run.

The watch procedure starts the development loop. Keep build commands in that guide rather than a second local script.

Try one edit at a time

Start with a task name entered and Complete selected. Change the heading's font size or an existing color value. An accepted in-place edit should preserve the field, toggle, state, and native control identities.

Change an existing handler body. Later events should use the new body without accumulating another subscription. Changing an initializer is different: it changes the structural signature.

Add a new node or reorder a style declaration. The host should replace the window or the watcher should restart the process. Transient task state then resets. This is expected behavior, not failed persistence: the tutorial has no persistence layer.

Know which edits preserve state

Edit	Expected handling
Existing text or supported property expression	In-place update when the runtime accepts the edit
Existing style value, resource value, or part rule value	In-place style refresh
Existing handler body	Later events use the updated method
Control types, parents, parameters, or Content identity	Structural replacement
State schema or initializer	Structural replacement
Added or removed event, style binding, or local property binding	Structural replacement
Style or resource names and declaration order	Structural replacement

The .NET runtime can require a process restart for additional unsupported edits. Do not promise that every property edit will preserve state in every runtime situation. See the full reload contract.

Diagnose failures at the right layer

Symptom	Check
XUI001 during compilation	Read the .xui location; check syntax, style target, part, property type, and value bounds
C# method or type error	Check generated callback signatures, namespace imports, and the real binding API
Native DLL load failure	Match the process architecture and DLL; use the configured output directory or DLL search path
Missing native export	Rebuild the DLL from the same source revision as the bindings
Wrong-thread exception	Move the UI call to the creating thread through an explicit delivery mechanism
Owner or parent error	Use an unattached element from the same Window
Callback failure	Preserve the reported exception or status; fix the failing callback rather than ignoring it
Style appears unchanged	Check local overrides, active theme, high contrast, and whether that part supports the property

An invalid style must not replace the previous valid style. A recoverable property error can leave the old window usable. Some generation failures require a restart, so do not assume state always survives an invalid edit.

Do not delete generated files to make a valid source edit take effect. Do not suppress all exceptions around Run. See binding errors for native status and wrapper behavior.

Continue with delivery and accessibility.