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The Role of COM+/Enterprise Services

DCOM alone did little more than define a way to establish a communication channel between two

pieces of COM-based software. To fill in the missing pieces required for building a feature-rich

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distributed computing solution, Microsoft eventually released Microsoft Transaction Server (MTS),

which was subsequently renamed to COM+ at a later release.

Despite its name, COM+ is not only used by COM programmers—it is completely accessible to

.NET professionals. Since the first release of the .NET platform, the base class libraries provided a

namespace named System.EnterpriseServices. Here, .NET programmers could build managed

libraries that could be installed into the COM+ runtime in order to access the same set of services as

a traditional COM+-aware COM server. In either case, once a COM+-aware library was installed into

the COM+ runtime, it was termed a 

serviced component.

COM+ provides a number of features that serviced components can leverage, including trans-

action management, object lifetime management, pooling services, a role-based security system, a

loosely coupled event model, and so on. This was a major benefit at the time, given that most dis-

tributed systems require the same set of services. Rather than forcing developers to code them by

hand, COM+ provided an out-of-the-box solution. 

One of the very compelling aspects of COM+ was the fact that all of these settings could be

configured in a declarative manner using administrative tools. Thus, if you wished to ensure an

object was monitored under a transactional context or belonged to a particular security role, you

simply needed to select the correct check boxes.

While COM+/Enterprise Services is still in use today, this technology is a Windows-only solu-

tion that is best suited for in-house application development or as a back-end service indirectly

manipulated by more agonistic front ends (e.g., a public website that makes calls on serviced com-

ponents [aka COM+ objects] in the background).