Service Lifetimes #

Lamar's service lifetime support exactly reflects the behavior of the ASP.Net Core DI container, as described in this article. This behavior is different than the older StructureMap lifecycle logic.

The supported life-cycles are:

1. Singleton -- Only one object instance is created for the entire application
2. Scoped -- Only one object instance is created for a container, whether that is the root container or a scoped (nested) container. This maps to StructureMap's ContainerScoped lifecycle
3. Transient -- A new object instance is created for every single request, including dependencies. This behavior is not consistent with StructureMap's old Transient and maps to StructureMap's old AlwaysUnique lifecycle

There is no equivalent in Lamar to StructureMap's version of Transient or the rarely used ThreadLocal lifecycle. HttpContext related scopes are no longer supported, with the assumption that Scoped is a useful replacement for HTTP request scoping of services.

Here are some sample usages of registering services with a lifetime:

public class LifetimeRegistry : ServiceRegistry
{
    public LifetimeRegistry()
    {
        // Lifetimes the ASP.Net Core way
        // The registration methods are all extension
        // methods, so hence, "this."
        this.AddTransient<IWidget, AWidget>();

        this.AddSingleton<IClock, Clock>();

        this.AddScoped<IUnitOfWork, UnitOfWork>();

        // Lifetimes the old StructureMap way
        // Transient is the default
        For<IWidget>().Use<AWidget>();

        For<IClock>().Use<Clock>().Singleton();

        // or

        ForSingletonOf<IClock>().Use<Clock>();

        For<IUnitOfWork>().Use<UnitOfWork>().Scoped();
    }
}

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