State transition table

Namespace: DesignPatterns.Behavioral

Overview

Model finite state graphs as (current state, trigger) → next state. Use a manual builder or compile-time [StateMachine] / [Transition] attributes to avoid hand-written switch blocks and catch invalid edges at build time.

This is not a full UML state-machine framework (no hierarchical states, history, persistence, or entry/exit action DSL).

Runtime

• ITransitionTable<TState, TTrigger> — TryTransition, GetAllowedTriggers, CanTransitionFrom
• TransitionTableBuilder<TState, TTrigger> — WithInitial, Add, Build
• Transition() extension — throws InvalidTransitionException on invalid edges

TState and TTrigger must be enums (v1).

var table = new TransitionTableBuilder<OrderStatus, OrderTrigger>()
    .WithInitial(OrderStatus.Draft)
    .Add(OrderStatus.Draft, OrderTrigger.Submit, OrderStatus.Submitted)
    .Add(OrderStatus.Submitted, OrderTrigger.Pay, OrderStatus.Paid)
    .Build();

table.TryTransition(OrderStatus.Draft, OrderTrigger.Submit, out var next);

Source generator

1. Define separate state and trigger enums.
2. Declare a static partial holder class with [StateMachine(typeof(TState), typeof(TTrigger), Initial = ...)].
3. Add one or more [Transition(from, trigger, to)] attributes on the holder.

[StateMachine(typeof(OrderStatus), typeof(OrderTrigger), Initial = OrderStatus.Draft)]
[Transition(OrderStatus.Draft, OrderTrigger.Submit, OrderStatus.Submitted)]
[Transition(OrderStatus.Submitted, OrderTrigger.Pay, OrderStatus.Paid)]
public static partial class OrderMachine;

// Generated: OrderStatusTransitionTable.Instance
// Holder:    OrderMachine.TryTransition(...), OrderMachine.InitialState

Diagnostics

DP026–DP031 — duplicate edges, invalid enum members, invalid holder, isolated states. See Diagnostics.

Sample

DesignPatterns.Samples.State

Maintainer doc: docs/StateTransitionTable.md (中文).