Server Error in '/' Application.

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Unable to generate a temporary class (result=1).
error CS2001: Source file 'C:\WINDOWS\TEMP\xxxxxx.cs' could not be found
error CS2008: No inputs specified

A: This error means that IIS_WPG group doesn't have Read and List Folder Contents permissions on C:\Windows\Temp folder on the server where DNP Portal is running. Just add IIS_WPG group with Read and List Folder Contents permissions on the mentioned folder on the DNP Portal server.

Please note that you should grant permissions to the domain IIS_WPG group if DNP Portal is running on domain controller or local IIS_WPG group in other cases.

Also note that it is good practice to grant those permissions to IIS_WPG on C:\Windows\Temp folder (or another folder in case of non-standard Environment Variables settings) on all servers running any DNP component.