Dec 05, 2018 03:12 AM|Ackerly Xu|LINK
What authentication are you using in application?FormsAuthentication or WindowsAuthentication?
Have your application thrown any error?
You say the code suddenly stopped and throw null value.
Do you mean HttpContext.Current.User is null?
If it is the case , you could refer to the link below
Please post your web.config and your related code.