Hi Alessandro,
Thank you for using Syncfusion products.
We have analyzed your requirement for "Highlighting text while search all occurrences in the EditControl". The highlight feature is not available in our product, but we can search the text using “Find and Replace DialogWindow”. We have also prepared a sample. In this sample, while searching all the occurrences of word or literal in the EditControl it displays all occurrences with line number in the "Find Symbol Results" box. You can refer all occurrences of text or literal from here.
Please download the sample from the below location.
Sample:
EditControlSampleRegards,
Priyanga B