IProcessManagerPropertyMapper

Overview

IProcessManagerPropertyMapper is the surface the framework hands to an IProcessHandler so it can declare how inbound messages correlate to persisted saga state. Each ConfigureMapping call registers one mapping expression; the framework compiles the expressions and uses them when loading a record through IProcessManagerFinder. Reach for this type only when you are overriding IProcessHandler<TData, TMessage>.ConfigureMapper — the default mapping (CorrelationId to CorrelationId) is usually right.

See Process Manager for the conceptual tour.

Reference

public interface IProcessManagerPropertyMapper

Mappings

IReadOnlyList<ProcessManagerToMessageMap> Mappings { get; }

Gets the mapping entries registered through ConfigureMapping. The framework enumerates this list when resolving a saga record for an inbound message; each entry carries the message type, the compiled message-property accessor, and the process-manager property path.

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ConfigureMapping

void ConfigureMapping<TProcessManagerData, TMessage>(
    Expression<Func<TProcessManagerData, object>> processManagerProperty,
    Expression<Func<TMessage, object>> messageExpression)
    where TProcessManagerData : IProcessManagerData
    where TMessage : Message;

Adds a mapping between a process-manager property and a message property. The framework records both expressions so the property-mapper instance becomes the declarative source of truth for “which property on TMessage locates the TData record.”

Parameters

• processManagerProperty — an expression selecting the state property to match against, for example d => d.OrderId.
• messageExpression — an expression selecting the message property to read, for example m => m.OrderId.

Remarks. The expressions must be simple property accessors — the framework parses the expression tree to derive both the compiled accessor and the property name/hierarchy used by the persistence layer. Method calls and arithmetic are not supported.

Throws. InvalidOperationException when a mapping for the same TMessage has already been registered. Each message type maps to at most one process-manager-data correlation, so duplicate registration is rejected loud rather than overwriting silently.

Usage

Correlating on an order number instead of the default correlation id

public sealed class ShippingSaga :
    IProcessHandler<ShippingSagaData, OrderPlaced>
{
    public Task HandleAsync(OrderPlaced message, ShippingSagaData data, IConsumeContext context, CancellationToken cancellationToken = default)
    {
        data.OrderId = message.OrderId;
        return Task.CompletedTask;
    }

    void IProcessHandler<ShippingSagaData, OrderPlaced>.ConfigureMapper(
        IProcessManagerPropertyMapper mapper)
    {
        mapper.ConfigureMapping<ShippingSagaData, OrderPlaced>(
            d => d.OrderId,
            m => m.OrderId);
    }
}

Override ConfigureMapper as an explicit interface implementation on the handler class and call ConfigureMapping once per (TData, TMessage) pair you want to correlate. The framework will look up the ShippingSagaData record by matching OrderPlaced.OrderId against ShippingSagaData.OrderId instead of the default CorrelationId-to-CorrelationId match.

See also

• Process Manager — concept
• IProcessHandler — related reference