It is by design that SfDiagram WinRT updates the Layout in its loaded event (i.e. Data for Layout are assigned before that). After analyzing your sample, we came to know that Data for Layout is assigned in Page loaded event (after Diagram is loaded). So, the Layout does not get refreshed. In order to solve this problem, Layout can be updated manually after data assigned.
Please let us know if you have any concerns
We have considered requirement as feature request “Support to update Layout automatically when collection changed”. However to access this, we request you to create your customer account in Direct Trac and open a new incident so that our support engineer will assist you accordingly.
Our Direct Trac support system can be accessed from the following link:
Please let us know if you any concerns