ERD (Entity-Relationship Diagram) Family

ERD family: entities, attributes and relationships

Overview
Node Types
Connection Points
Connection Conventions
Usage Example

Overview

Base Control: ERDControl : MaterialControl
Namespace: Beep.Skia.ERD

The ERDControl is the root control for this diagram family. It inherits MaterialControl and provides shared port management, styling, and template methods for all nodes in the family.

This family contains 4 node types.

Node Types

Node Class	Shape	Description
`ERDEntity`	Table rectangle	Database table with columns, primary keys, foreign keys, and row-level connection points for per-column relationships.
`ERDAttribute`	Oval	Entity attribute with name, data type, and nullable flag.
`ERDRelationship`	Diamond	Relationship between entities with cardinality (1:1, 1:N, M:N) and Crow's Foot notation.
`DDLExporter`	N/A (utility)	Generates CREATE TABLE SQL from ERDEntity definitions including PKs, FKs, indexes, and constraints.

ERDEntity

Database table with columns, primary keys, foreign keys, and row-level connection points for per-column relationships.

Shape	Table rectangle
Input Ports	2+ (left)
Output Ports	2+ (right)

ERDAttribute

Entity attribute with name, data type, and nullable flag.

Shape	Oval
Input Ports	1
Output Ports	1

ERDRelationship

Relationship between entities with cardinality (1:1, 1:N, M:N) and Crow's Foot notation.

Shape	Diamond
Input Ports	2+ (left/top)
Output Ports	2+ (right/bottom)

DDLExporter

Generates CREATE TABLE SQL from ERDEntity definitions including PKs, FKs, indexes, and constraints.

Shape	N/A (utility)
Input Ports	—
Output Ports	—

Connection Points

Every node in this family exposes connection points (ports) for linking to other nodes. Port positions are computed lazily by LayoutPorts(), which runs when MarkPortsDirty() flags the layout as stale after a move or resize.

Node Class	Input Ports	Output Ports	Extra
`ERDEntity`	2+ (left)	2+ (right)	1 per field (left/right)
`ERDAttribute`	1	1	—
`ERDRelationship`	2+ (left/top)	2+ (right/bottom)	—
`DDLExporter`	—	—	—

Connection Conventions

When building diagrams with this family, follow these conventions:

ERDEntity uses row-level connection points for per-column relationships
Multiplicity markers displayed on line endpoints (1, N, M)
DDLExporter generates SQL from entity metadata
ConnectionPoint.DataType and RowId enable schema validation

Usage Example

Complete example showing creation, node placement, and connection:

C# Example

var erd = new ERDControl
{
    X = 100, Y = 50,
    Width = 700, Height = 500
};
drawingManager.AddComponent(erd);

var entity = new ERDEntity
{
    X = 200, Y = 100,
    TableName = "Customers",
    Width = 200, Height = 150
};
entity.AddField("Id", "int", isPrimaryKey: true);
entity.AddField("Name", "varchar(100)");
entity.AddField("Email", "varchar(255)");
drawingManager.AddComponent(entity);

var attr = new ERDAttribute
{
    X = 450, Y = 100,
    AttributeName = "Email",
    DataType = "varchar(255)"
};
drawingManager.AddComponent(attr);

var rel = new ERDRelationship
{
    X = 200, Y = 300,
    RelationshipType = RelationshipType.OneToMany,
    Text = "places"
};
drawingManager.AddComponent(rel);

// Row-level connections with multiplicity
drawingManager.ConnectComponents(entity.GetFieldPoint("Id"), rel.InPoints[0]);
drawingManager.ConnectComponents(rel.OutPoints[0], attr.InPoints[0]);

// Export DDL
var exporter = new DDLExporter();
string sql = exporter.Export(entity);