The observed by you behavior is an expected one when the ExcludedFromLayoutSave
attached property is set to True
. The pane that has that property set to True will be skipped when the layout is saving and when loading the layout later, the Pane wont' exist anymore as you have observed - only the Panes that are saved and loaded from the XML file will exist.
What we could suggest you as one possible approach to achieve the desired is to try to create the Pane in the code behind after the LoadLayoutFromString is called and the layout is loaded completely.
We would like also to inform you that a new feature that will allow writing custom save/load layout logic is under development and should be released with Q2 2016. Using it you will be able to implement a new logic for saving the panes and loading them. You could follow the item for the feature on the following link:
Hope the provided information will be helpful for you.
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