State diagrams

A StateDiagram draws states linked by transitions (Mermaid stateDiagram-v2):

var diagram = new StateDiagram();
var start = diagram.AddState("start", kind: StateKind.Start);
var draft = diagram.AddState("Draft");
var review = diagram.AddState("Review");
var published = diagram.AddState("Published");
var end = diagram.AddState("end", kind: StateKind.End);

diagram.AddTransition(start, draft);
diagram.AddTransition(draft, review, "submit");
diagram.AddTransition(review, draft, "reject");
diagram.AddTransition(review, published, "approve");
diagram.AddTransition(published, end);
diagram.AddNote(review, "Two approvals are required");

States

The Kind of a StateDiagramState sets its shape: a rounded rectangle, a start (a filled circle) or an end (a filled circle in a ring), a choice (a small diamond), a fork or a join (a bar across the flow). A StateNote is drawn on the left or the right of its state.

Composite states

A state with Regions is a composite state: a frame with its name, around its states. AddState adds a state to its last region. Several regions are concurrent parts, drawn side by side in dashed frames:

var diagram = new StateDiagram();
var active = diagram.AddState("Active");

// A composite state with two concurrent regions
var numLockOff = active.AddState("NumLockOff");
var numLockOn = active.AddState("NumLockOn");
active.Regions.Add(new StateDiagramRegion());
var capsLockOff = active.AddState("CapsLockOff");
var capsLockOn = active.AddState("CapsLockOn");

diagram.AddTransition(numLockOff, numLockOn, "press");
diagram.AddTransition(numLockOn, numLockOff, "press");
diagram.AddTransition(capsLockOff, capsLockOn, "press");
diagram.AddTransition(capsLockOn, capsLockOff, "press");

A composite state can have its own Direction, which applies when no transition crosses its border, as for the subgraphs of a flowchart.

Mermaid syntax

var diagram = (StateDiagram)MermaidDocument.Parse("""
    stateDiagram-v2
        [*] --> Still
        Still --> Moving : push
        Moving --> Still
        Moving --> Crash
        Crash --> [*]
    """).Content;

[*] is the start state of the region when a transition leaves it, and its end state when a transition enters it; each region of a composite state has its own. The parser also reads the descriptions (state "Description" as id, id : description), the kinds (state id <<choice>>, <<fork>>, <<join>>), the composite states (state id { ... }, with -- between concurrent regions), the notes (note right of id : text, or on several lines up to end note), direction, classDef, class, :::class and style.