Basically this problem comes up when we work with Asp.Net Application With IIS Server. I got this error while working with Asp.Net MVC Application. When I run My MVC application suddenly I got this error:
“System.Data.SqlClient.SqlException was unhandled by user code: Login failed for user 'IIS APPPOOL\DefaultAppPool’” and database connection couldn't open.
There are some step for solving this problem.
- Go to your Run Window and there you type “Inetmgr” and click oK ( Means Go to IIS Server).
- Here you will IIS Server window , from this window you go to “Application pools” and then select “DefaultAppPool” Right click on it and select “Advance Settings” and click on that.
![Advance Settings]()
- When you will click on Advance settings link it will open Advance setting window there you select “Identity” (In Process Modal) and Change the path from ApplicationPoolIdentity to LocalSystem.
![path]()
When you click on this Path, three dotted buttons, a window will open from there “Built-in-Account “radio button contain a dropdown box , from this dropdown box you change this path and the click OK.
![built]()