Implementation of IsPostBack in page load

Question

The more I use ASP.NET, the more if (!IsPostBack) {} seems pointless...

First example:

For example, I just Googled an issue, they said use this

Answer 1

When there is no need to repeat the operation other than the first time.

use it with expensive operations (such as getting data from a database or populating ListItems) that must be performed only the first time the page or control is loaded. If the page is posted to the server and then reloaded, there is no need to repeat the operation. By testing the value of IsPostBack, you can skip the expensive operation,