im using this method to read content as IPublishedContent

_context.UmbracoContext.Content.GetById(IContent.key)

but sometimes this method returns null or wierd errors ? when the object is actually published an stored in database. i need to read content and the nested childs And IContent doesent provide any Extensions to read
Descendants. How is this cached updated ? How can i work with live data and their realeted Descendants? Im following this example

but is use this code on ContentService_Published event https://our.umbraco.com/documentation/getting-started/Code/Subscribing-To-Events/