ExportUml

The Lite.StateMachine offers the ability to export UML of your state machine into the Graphviz (DOT graph) format. This is useful for documentation, discovering bugs early on, your blog posts, and more. The ExportUml(..) method features options to customize your graphs the way you see fit.

Parameter Options

string ExportUml(...);

Parameter	Default	Description
IEnumerable<TStateId>? initialStateIds	null	Entry-point initial state(s) at the top-level.
bool includeLegend	true	Include a legend subgraph that explains shapes and colors.
IDictionary<Result, string>? transitionColors	null	Color overrides for Result-based transitions.
string parentToChildColor	"Green"	Color used for parent → initial-child transition edges (default "Green").
string graphName	"StateMachine"	Title of the graph (default "StateMachine").
bool rankLeftToRight	true	Display as left-to-right layout or top-to-bottom.
Func<TStateId, string>? nodeLabelSelector	null	Optional label selector for nodes.
string? legendText	null	Optional custom legend description text.
bool showParentInitialEdge	true	Whether to also draw the parent → initial-child edge (green, labeled "initial") for composite parents.

Usage Examples

Basic Export With Legend

var machine = new StateMachine<StateId>()
  .RegisterState<BasicState1>(StateId.State1, BasicStateId.State2)
  .RegisterState<BasicState2>(StateId.State2, BasicStateId.State3)
  .RegisterState<BasicState3>(StateId.State3);

var dot = machine.ExportUml(includeLegend: true, graphName: "Basic State Machine");
System.IO.File.WriteAllText("machine.dot", dot);

Set Initial State

Option to set a single or multiple initialStateId.

string dot = sm.ExportUml([StateId.State1], includeLegend: true);

Use-case architecture example of multiple starting points:

if (appLicense == License.Pro)  await machine.RunAsync(StateId.EntryProState);
if (appLicense == License.Demo) await machine.RunAsync(StateId.EntryDemoState);

// To set multiple initial states:
string dot = sm.ExportUml([StateId.EntryProState, StateId.EntryDemoState]);

Override Transition Colors

// Override transition colors & keep parent→initial edge (green)
var customColors = new Dictionary<Result, string>
{
  [Result.Ok]      = "#1E90FF", // DodgerBlue
  [Result.Error]   = "gold",
  [Result.Failure] = "#FF3B30"
};

string dot = machine.ExportUml(
  initialTopLevelStates: [StateId.State1],
  includeLegend: true,
  transitionColors: customColors,
  parentToChildColor: "green3");

Export as SVG/PNG

Rendering DOT → SVG or PNG with Graphviz

using System.Diagnostics;

// Build DOT
string dot = sm.ExportUml([StateId.State1], includeLegend: true);

// Render to SVG
var psi = new ProcessStartInfo
{
  FileName = "dot",
  Arguments = "-Tsvg -o machine.svg",
  RedirectStandardInput = true,
  RedirectStandardError = true,
  UseShellExecute = false,
  CreateNoWindow = true
};

using var proc = Process.Start(psi)!;
proc.StandardInput.Write(dot);
proc.StandardInput.Close();
string err = proc.StandardError.ReadToEnd();
proc.WaitForExit();

if (proc.ExitCode != 0)
  throw new InvalidOperationException($"Graphviz failed ({proc.ExitCode}): {err}");
// For PNG, change Arguments: "-Tpng -o machine.png"