__doPostBack is not defined

Question

Im getting that error when try to call a __doPostBack on one of my pages, every page that i have in the project use __doPostBack function but in this particular page im gett

Answer 1

For me it was the fact that I was using a custom User-Agent Header of User-Agent: This is a Test, please ignore.

This is because IIS ASP.NET Webforms generates web pages depending on the User-Agent string.

To fix it, I included the browser types, plus a message at the end, i.e.

User-Agent: Mozilla/5.0 (X11; Linux x86_64) Chrome/75.0.3770.80 (This is a Test, please ignore)

And the page started running correctly again.