The Step Pipeline

What Steps Are

NOF applications are assembled from small, ordered units of work called steps. A step is either:

• a service registration step that runs while the DI container is being built
• an application initialization step that runs after the host is constructed

The framework executes these steps in dependency order.

Core Contracts

public interface IAfter<TDependency>;
public interface IBefore<TDependency>;

public interface IServiceRegistrationStep
{
    ValueTask ExecuteAsync(IServiceRegistrationContext builder);
}

public interface IApplicationInitializationStep
{
    Task ExecuteAsync(IHost app);
}

Ordering Model

Ordering is declared through marker interfaces:

• IAfter<T> means the current step must run after T
• IBefore<T> means the current step must run before T

NOF builds a dependency graph from the registered step instances and executes them in topological order.

Registration and Initialization

NOFAppBuilder<T> keeps two collections internally:

• service registration steps
• application initialization steps

During BuildAsync() it:

1. adds framework defaults such as auto-inject registration and hosting defaults
2. executes all service registration steps in dependency order
3. builds the host
4. executes all initialization steps in dependency order

Practical Guidance

• Use a registration step when you need to add or configure services.
• Use an initialization step when you need the fully built host or endpoint pipeline.
• Use TryAddRegistrationStep(...) or TryAddInitializationStep(...) when duplicate registration should be ignored.
• Use RemoveRegistrationStep(...) or RemoveInitializationStep(...) when a host wants to replace a default behavior.