The Kendo documentation does not explicitly state this limitation of the custom fields names, when used in a Scheduler HTML helper. Having that said, we will need include that in the Custom editors how-to article
I will try to explain a bit the reason behind the discussed limitation. The SchedulerAjaxDataSourceBuilder
uses a predefined Schema
for the data source, that translates all the fields from the ISchedulerEvent interface to the corresponding lower-case fields in the widget data. The Builder, however, does not allow configuration of the Schema for custom fields. Therefore, they would be used as they are defined in the implementation class of the ISchedulerEvent.