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Access to Printers Within a Web Application (IIS)

(combit Team) #1
Valid from List & Label 16
A system requirement for List & Label is to have an installed printer driver. List & Label works closely with the Windows-GDI and therefore requires a printer driver device context for all operations. Therefore the Microsoft XPS Document Writer printer driver (is automatically installed with the .NET Framework 3.5) could be used as a reference printer. In addition, the installed printer driver has to be accessible in the current application or user context. This requirement is implicity fulfilled with most of the desktop applications by the logged on Windows user. Please note that the application or user context for a web application differs from a normal desktop application: The web application will be executed on the server and could have a different application or user context, especially in an Internet Information Services (IIS) environment.
As the process, service or web application will be executed in an IIS context it is important to note that the used ApplicationPool will be configured to have explicit access to the installed printer driver of the server. For IIS versions 7.0/7.5 (Windows 7/Windows Server 2008 R2 and above) the default identity is the "ApplicationPoolIdentity" which is a dynamically created virtual account which could not have access to system ressources, especially to the installed printers and their drivers. In this case you have to change the identity of the ApplicationPool to an existing system (e.g. LocalService, LocalSystem, NetworkService) or a separate user account.
You can find detailed information in the following link and the related knowledgebase articles beneath this description.



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