c# - "Page.IsValid cannot be called" occurs in Page_PreRender event handler -

I am currently learning ASP.NET, and read that the page comes after the verification page. When I put it (page .isiidid == true) whatever,

Then I get an error, even if that line is in my page_reender () event handler.

How does this make sense?

Thanks in advance, just trying to understand it completely.

You should be in control, who is posting () for verification or actually accessing Manually calls for ... otherwise verification has not been done, so there is nothing to check, the value will be meaningless, which is the current error you are seeing.