SchematicNeo4j.Attributes 5.0.1

SchematicNeo4j

A code-first approach to manage a consistent Neo4j graph schema for a domain layer that is defined in a .NET library.

For Developers

New in version 5.0.0

• Relationship Attributes and Relationship Range Index.
• Added default and user specified names for indexes and constraints.
• Added NodeKeyName to the NodeAttribute, allowing for override of the default nk{firstLabel}.
• Keeps consistency check by entityName and properties. Covers cases where existing constraints or indexes may already have a generic name from being defined in v3.

Upcoming in the next minor release

• Index types other than Range Indexes.

Future change

• potentially breaking change Changing Extension and CRUD methods to a Fluent pattern to make method discovery and use easier.
  • typeof(Class1).Label() makes autocomplete method discovery difficult. I'd like to simplify that.
• methods to list schema for export and comparison.

Using Range Index

Relationship Range Index was added in v5.0.0 and works the same as Indexes on Nodes, except that it ignores the Label and IsAbstract properties. The Indexes.Create() logic uses the class level attribute to differentiate between Relationship | Node.

[Relationship]
public class PlaysFor {

	[Index()]
	[Index(Name="PlaysFor_YearPosition")]
	public int Year { get; set; }
	
	[Index(Name="PlaysFor_YearPosition")]
	public string Position { get; set; }
}

[Node(Label="Person:Player")]
public class Player : Person {
  [Index(Label="Player")]
  public string Postion {get; set;}
}

Example creates 3 Indexes (all range indexes by default): 1. Relationship Range Index with default name idx_PlaysFor_Year 2. Relationship Range Index with name PlaysFor_YearPosition 3. Node Range Index with name idx_Player_Position

Defining your domain schema (RELATIONSHIPS)

Identifying Relationships

Annotate the class with a RelationshipAttribute (optionally provide a Type, defaults to the class name in proper format).

[Relationship]
public class PlaysFor {}

[Relationship(Type="PLAYS_FOR")]
public class Class1 {}

Results for both are ()-[:PLAYS_FOR]-()

Defining your domain schema (NODES)

Identifying Nodes and their Node Key

Annotate the class with a NodeAttribute (or it can also default to the class name)

[Node(Label = "Person")]
public class Class1 {}

public class Person {}

[Node]
public class Person {}

Annotate the properties that make up the Node Key

public class Car {
  [NodeKey]
  public string Make { get; set; }

  [NodeKey]
  public string Model { get; set;}
}

Name your NodeKey; useful in cases of existing constraints or your project uses a specific naming convention. The default is nk[firstLabel].

[Node(Label="Car:Vehicle", NodeKey="nkCar")]
public class Car {
  [NodeKey]
  public string Make { get; set; }

  [NodeKey]
  public string Model { get; set;}
}

Using Shared (or inherited) Node Keys

If you want to differentiate between 2 subclasses of an object but they are going to share the same node key, defined by the super class. We can do something like this.

public class Person {
  [NodeKey]
  public string FirstName { get; set; }

  [NodeKey]
  public string LastName { get; set;}
}

[Node(Label="Person:Coach")]
public class Coach : Person {
  public int YearStarted {get; set;}
}

[Node(Label="Person:Player")]
public class Player : Person {
  public string Postion {get; set;}
}

Both players and coaches have a name; players can be coaches, and vice versa. Either way, this keeps our data clean preventing a person from having 2 records in the system.

SchematicNeo4j.Extensions

There are a few provided extensions that we can take advantage of when using the CustomAttributes. Assume the following Vehicle definition:

public class Vehicle {
  [NodeKey]
  public string Make { get; set; }

  [NodeKey]
  public string Model { get; set;}

  [NodeKey]
  public string ModelYear { get; set; }

}

We can get the Label by:

// for a type
var theLabel = typeof(Vehicle).Label();

We can get the Node Key properties by:

// for a type
List<string> vehicleNodeKey = typeof(Vehicle).NodeKey();

We can get the Node Key Name by:

// for a type
string vehicleNodeKeyName = typeof(Vehicle).NodeKeyName();

Using SchematicNeo4j.Schema.Initialize

Once we have our domain models identified we can use the Schema methods to put it into the graph. You can pass in either an entire assembly, a list, or a single Type. This will create the indexes for both entity types, node and relationship.

// Pass an Assembly and driver
SchematicNeo4j.Schema.Initialize(assembly:Assembly.GetAssembly(typeof(DomainSample.Person)), driver);

// Pass a list of domain types
  // Get this assembly
  Assembly a = Assembly.GetExecutingAssembly();
  // Limit to a specific namespace.
  var listOfTypes = a.ExportedTypes.Where(t => t.Namespace == "MyExecutingThing.MyDomain").ToList();
  SchematicNeo4j.Schema.Initialize(listOfTypes, driver);