UML Class Diagram

Controls.UmlClassDiagram(classes, relations) draws a UML class diagram. Each class is a box with a header and an attribute compartment. The header holds an optional «stereotype», the name, and the package of a foreign class. Each attribute line reads name : Type [multiplicity].

Classes are joined by relations:

A box with an Href is a link.

var (classes, relations) = UmlSchemaProjection.FromContentSchemas(
    typePaths.Select(p => new UmlSchemaInput(p, schemaOf(p))),
    path => $"/DataModelling/Explorer/Type/{Uri.EscapeDataString(path)}");
return Controls.UmlClassDiagram(classes, relations).WithMaxAttributes(6);

The model is the schemas

UmlSchemaProjection.FromContentSchemas reads the JSON schemas @{type}/schema/ publishes:

• Attributes. Every property except $type is an attribute. An array is [*] and a nullable value is [0..1]. The description is the property's XML doc.
• Relations. A property carrying x-meshNode (a [MeshNode("nodeType:…")] reference) becomes an association to each nodeType:{Path} it names. The association is labelled with the property name, and its target multiplicity is *, 0..1 or 1.
• Foreign classes. A referenced type that is not one of the inputs becomes a foreign class labelled with its package, so references across plugins show.

The projection needs no CLR type and no instance. It is the same answer the schema read gives an agent.

The geometry is pure

UmlClassDiagramControl.Layout is a layered (Sugiyama-style) layout, unit-tested in UmlClassDiagramTest:

• Layers. A referenced class or a part sits below the class that references or owns it. A base class sits above its subclass, because UML draws the triangle up.
• Cycles are broken by reversing the back edges of a depth-first walk in input order.
• Order within a layer comes from four barycentre sweeps, with ties kept in input order.
• Edges are orthogonal. Each box spreads its ports so parallel edges do not coincide.
• Guarantees: no two boxes overlap, and the canvas encloses every box and route.

Renderers only draw what Layout returns. Every view of the same model therefore draws the same picture, and a renderer needs no JavaScript layout engine.

The layout is computed in C# rather than with a bundled JS engine (ELK, dagre) for three reasons:

• it is deterministic and testable without a browser;
• it runs where the data is;
• it adds no script asset to the portal.

The platform already ships Mermaid, but it lays out its class diagrams itself and gives a caller no control over notation or interaction.

Size

WithMaxAttributes(n) caps the attribute lines per box; the rest read + n more. For a large model, pass the classes the page is about plus their direct neighbours rather than the whole package.

Open vocabularies (string constants, never enums): UmlClassKind (local, foreign, featured) and UmlRelationKind (association, composition, generalization). A renderer draws a value it does not know plainly.