When you update the form fields inside the Grid programmatically, the widget is not aware of this. As a result, the underliying data items are not updated either, and when the Update button is clicked, there is nothing to update. The editing mechanism does not take the form field values when the Update button is clicked. Instead, it relies on MVVM and two-way binding, which updates the data item when a change event of a form field is fired. That's why you can trigger this event manually for each form controls that has its value changed via script.
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