Professional Visual Basic 2012 and .NET 4.5 Programming

Characteristics of a Windows Service

To properly design and develop a Windows Service, it is important to understand how it differs from a typical Windows program. Here are the most important characteristics of a Windows Service:

• It can start before a user logs on. The system maintains a list of Windows Services, which can be set to start at boot time. Services can also be installed such that they require a manual startup and will not start at bootup.
• It can run under a different account from that of the current user. Most Windows Services provide functionality that needs to be running all the time, and some load before a user logs on, so they cannot depend on a user being logged on to run.
• It has its own process. It does not run in the process of a program communicating with it.
• It typically has no built-in user interface. This is because the service may be running under a different account from that of the current user, or the service may start at bootup, which means that calls to put up a user interface might fail because they are out of context.
• Under certain operating systems, activities permitted in normal programs are not allowed in Windows Services. For example, you can play a sound from a Windows Service in Windows XP, but you cannot do so in Windows Vista, Windows Server 2008, or Windows 7.
• User interaction with the service is accomplished either via a built-in Windows program, the Service Control Manager, or using a special external program you develop. Creation of ...