To specify the COM+ application’s activation type, you can use the ApplicationActivation assembly attributes. You can request that the application be a library or a server application:

[assembly: ApplicationActivation(ActivationOption.Server)]

or:

[assembly: ApplicationActivation(ActivationOption.Library)]

If you do not provide the ApplicationActivation attribute, then .NET uses a library activation type by default. Note that this use differs from the COM+ default of creating a new application as a server application.

Before I describe other serviced components attributes, you need to understand what attributes are. Every .NET attribute is actually a class, and the attribute class has a constructor (maybe even a few overloaded constructors) and, usually, a few properties you can set. The syntax for declaring an attribute is different from that of any other class. In C#, you specify the attribute type between square brackets [...]. You specify constructor parameters and the values of the properties you wish to set between parentheses (...).

In the case of the ApplicationActivation attribute, there are no properties and the constructor must accept an enum parameter of type ActivationOption , defined as:

enum ActivationOption{Server,Library}

There is no default constructor for the ApplicationActivation attribute.

The ApplicationActivation attribute is defined in the System.EnterpriseServices namespace. Your must add this namespace to your project references and reference that namespace in your assembly information file:

using System.EnterpriseServices;

The rest of this chapter assumes that you have added these references and will not mention them again.