Step 1 - Download and install Neo4j

I assumed that you have installed Java Runtime on your machine. If you haven't did it yet, please download JRE.

Go to http://neo4j.org/download and choose the latest version. 
Download and extract the contents to a suitable location.
Start the server by opening a command prompt, and running the command:

bin\neo4j start

If things are fine, enter to http://localhost:7474 on your browser. You will redirect to the administrative web application which provides some information of your database and a simple database navigation interface.

 

Step 2 - Start Coding!

Graph Objects

Neo4Net Graph node is represented by a class which derives GraphPropertyContainer. The node's default name is the class name, but you can define other name by using [GraphObject("{OBJECT_NAME}"] attribute.

The properties that you want to save in the graph must have GraphPropertyAttribute (similar to DataMemberAttribute in WCF).

For example, I created a Person object which represents a node with person's properties:
public class Person : GraphPropertyContainer { public Person() : base() { }

    [GraphProperty]
    public string Firstname { get; set; }

    [GraphProperty]
    public string Lastname { get; set; }
}

   And a KnowsRelation, reperesents a KNOWS relationships between nodes (=people).



[GraphObject("Knows")]
public class KnowsRelation : GraphPropertyContainer
{
    public KnowsRelation() : base() { }

    [GraphProperty]
    public DateTime CreationTime { get; set; }
}

Create a Graph-Context object

var graph = new GraphContext("http://localhost:7474/db/data/");

You can also store the database Url in the element (web.config) with "neo4j" name, and create the GraphContext without any parameter on the construction method.

Create the "Person"-nodes and connect them to the reference node with "KNOWS" relation

Person p1 = new Person()
{
    Firstname = "Steve",
    Lastname = "Jobs"
};

Person p2 = new Person()
{
    Firstname = "Steve",
    Lastname = "Ballmer"
};

//Creating graph nodes
var p1Node = graph.CreateNode(p1);
var p2Node = graph.CreateNode(p2);

//Connect the nodes with graph "KNOWS" relationship
graph.GetReferenceNode().CreateRelationshipTo(p1Node, new KnowsRelation() { CreationTime = DateTime.Now });
graph.GetReferenceNode().CreateRelationshipTo(p2Node, new KnowsRelation() { CreationTime = DateTime.Now });

I also connected Steve & Steve with "KNOWS" relation:
p1Node.CreateRelationshipTo(p2Node, new KnowsRelation() { CreationTime = DateTime.Now });

Traversing nodes, get node's properties and change them

The following code searches "Person"-nodes that connect with "KNOWS" relation and has a specific property-values: "Steve Jobs". Then it get the node's properties (based on Person object), change to "Eric Shmidt" and commit the changes in the graph.

// Get the "Steve Jobs" object and change it to "Eric Shmidt"
var node = graph.GetReferenceNode().TraverseNodes(Neo4Net.Core.TraversalOrder.DepthFirst, 1, x => x.Firstname == "Steve" && x.Lastname == "Jobs", typeof(KnowsRelation), Neo4Net.Core.Direction.Outgoing).FirstOrDefault();
if (node != null)
{
    var properties = node.GetProperties();
    properties.Firstname = "Eric";
    properties.Lastname = "Shmidt";
    node.CommitChanges(properties);
}

 

The powerful of graph-databases

Graph databases is great for social applications, not only because it can handles billions of data, but it offers a simple and flexible structure based on **relationships between objects, **similar to the real world.
If I'd like to know who are the people that Eric Shmidt knows, I just need to get the objects that connect to Eric with "KNOWS" relation!

// Get all the people that Eric Shmidt knows
var peopleThatEricKnows = p1Node.TraverseNodes(Neo4Net.Core.TraversalOrder.DepthFirst, 1, Neo4Net.Core.ReturnableEvaluator.AllButStartNode, typeof(KnowsRelation), Neo4Net.Core.Direction.Outgoing);

I can also get the opposite case, when I'd like to know who are the people that knows Eric.
Just change the direction from Outgoing to Incoming:

var peopleThatKnowsEric = p1Node.TraverseNodes(Neo4Net.Core.TraversalOrder.DepthFirst, 1, Neo4Net.Core.ReturnableEvaluator.AllButStartNode, typeof(KnowsRelation), Neo4Net.Core.Direction.Incoming);