Yes, it's possible to filter by the Categories field, you will need to use the extension method GetValue for that purpose. For example:
var importantCategoryId =
"your category ID"
List<Event> allEvents = App.WorkWith().Events().Get()
.Where(t => t.Status == ContentLifecycleStatus.Live)
.Where(t => t.GetValue<TrackedList<Guid>>(
).Contains( importantCategoryId ))
The GetValue() method will return a TrackedList of the category IDs assigned to that content item, so you'll need to check for the particular ID of that category.
Please note you'll need to add a reference to Telerik.Sitefinity.Model
All the best,
the Telerik team
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