Currently, there appear to be issues creating Setters within DataTemplates, where setting a specific Source Element works correctly, but its list of Properties doesn't reflect what the Element offers, until the document is closed and re-opened.

Repro Steps:

1) Create a Project featuring a MainPage.xaml

2) Introduce a ContentControl Element to the Page, and create a Content Template for it, saved to GlobalResources.

This will open the Template in the Inline Template Dummy Editor.

3) Remaining within the interior of the ContentControl Content Template, Introduce a Checkbox Element into its RootGrid, and name the Element. (required)

4) Navigate to the Interactivity/Setters Panel, and create a new Setter on the DataTemplate Root, of type "When Property Changes".
This will create a Setter, with a default IsMouseOver=True setting.

Observe how an immediate XAML error is thrown.

5) Clear the IsMouseOver Property causing this error, and save all documents.

6) For the created Setter, in the 'SourceName' Property, set it to the name of the Checkbox given to the Checkbox introduced in Step 3).

7) Under the 'Property' field of the Setter, select the Checkbox's "IsChecked" Property.

Observe how the "IsChecked" Property is not present in the list of available Properties to use.

8) Make no selection in this Property dropdown, then save, and close all open documents.

9) Re-Open the MainPage, and navigate back into the inline Template Editor for the ContentControl Content Template, and return back to its Interactivity/Setters Panel, and re-select the Setter created in Step 4).

10) Re-Open the Setter's 'Property' Dropdown, and identify the 'IsChecked' Property.

Observe how this time, the expected Property appears in the list.

Expected Results: Creating a Setter on a DataTemplate does not immediately generate a XAML error.

Expected Results: Setting a Source Element of "Checkbox" makes all applicable Checkbox Properties immediately accessible without restart of the Page.