Inject

Marks a public property to be filled from the container when a train is resolved through a Trax registration helper. ServiceTrain uses it for its own framework services (EffectRunner, JunctionEffectRunner, LifecycleHookRunner, Logger, ServiceProvider).

It is framework plumbing, not the way to give a junction or a train its dependencies. Use constructor injection for those.

Signature

namespace Trax.Effect.Attributes;
 
[AttributeUsage(AttributeTargets.Property)]
public class InjectAttribute : Attribute
{
    public InjectAttribute();
}

How it is filled

The Add*TraxRoute and Add*TraxJunction factories call IServiceProvider.InjectProperties(instance) after resolving the implementation. For every public instance property that carries [Inject] and has a setter:

Nothing else reads the attribute. A type resolved any other way (constructed with new, resolved by its concrete class, or a junction a train builds for itself in its chain) gets no property injection, and a junction's [Inject] properties stay null.

Example

// Do this: constructor injection
public class ChargePayment(IPaymentGateway gateway) : Junction<ValidatedOrder, PaymentReceipt>
{
    public override Task<PaymentReceipt> Run(ValidatedOrder order) =>
        gateway.Charge(order.CustomerId, order.Total, CancellationToken);
}
 
// Not this: the train builds the junction itself, so the property is never set
public class ChargePayment : Junction<ValidatedOrder, PaymentReceipt>
{
    [Inject] public IPaymentGateway? Gateway { get; set; }
    // ...
}

IServiceProvider.InjectProperties is public for Trax's own registration code and hidden from completion.

Package

dotnet add package Trax.Effect