The order in which the master page and content page triggers events, the rule that triggers the event is that the initialization event is from the innermost control to the outermost control, and the other event is from the outermost control to the innermost control.
Here is a test:
The first time the Init event for the master page is triggered.
The second time the Init event for the content page is triggered.
The third trigger is the Load event for the content page
The fourth time the load event for the master page is triggered
Summarize:
The order in which the master page and the content page trigger events:
1. master Page init event.
2. Content Page init event.
3. Content Page Load Event
4. master Page Load event.
5. Content Page PreRender event.
6. master Page PreRender Event
Event firing order in ASP. NET Master pages and content pages