How to create relationship between neo4j existing node and new node in C#.Net using Neo4jClient?

Question

I work on C#.net project with Neo4j database and unable to create relationship between existing node in Neo4j and new node using C#.Net.

I am creating nodes using following code

// Create entities
var refA = client.Create(new Person() { FName = "Person A" });
var refB = client.Create(new Person() { FName = "Person B" });
var refC = client.Create(new Person() { FName = "Person C" });
var refD = client.Create(new Person() { FName = "Person D" });

// Create relationships
client.CreateRelationship(refA, new KnowsRelationship(refB));
client.CreateRelationship(refB, new KnowsRelationship(refC));
client.CreateRelationship(refB, new HatesRelationship(refD, new HatesData("Crazy guy")));
client.CreateRelationship(refC, new HatesRelationship(refD, new HatesData("Don't know why...")));

Now i want to create relationship between one of the existing node getting from database using some condition and creating new node. But can't do this

Answer 1

If you wnat to be using Neo4J from C# you still need a solid understanding of Cypher.

You can find a very documentation about it here:

Cypher query language - documentation

I have created an example program for you creating 3 nodes and 2 relationships between them, then querying the nodes neigbouring node 1.

using Neo4jClient;
using Neo4jClient.Cypher;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Neo4JTest
{
    class Program
    {
        static void Main(string[] args)
        {
            try
            {
                GraphClient client = new GraphClient(new Uri("http://localhost:7474/db/data"));
                client.Connect();

                // Create nodes and relationship
                MyNode node1 = new MyNode() { Name = "Test 1" };
                MyNode node2 = new MyNode() { Name = "Test 2" };

                NodeReference<MyNode> node1ref = client.Create<MyNode>(node1);
                NodeReference<MyNode> node2ref = client.Create<MyNode>(node2);

                MyRelationShip rel12 = new MyRelationShip(node2ref);

                var Rel1 = client.CreateRelationship<MyNode, MyRelationShip>(node1ref, rel12);               

                MyNode node3 = new MyNode() { Name = "Test 3" };
                NodeReference<MyNode> node3ref = client.Create<MyNode>(node3);

                MyRelationShip rel13 = new MyRelationShip(node3ref);
                var Rel13 = client.CreateRelationship<MyNode, MyRelationShip>(node1ref, rel13);

                var query = client.Cypher.Start(new { n1 = node1ref })
                                        .Match("n1-[:MYRELATIONSHIP]->targetnode")
                                        .Return<MyNode>(targetnode => targetnode.As<MyNode>());
                var res = query.Results;

                int i = 0;
                foreach (MyNode n in res)
                {
                    i++;
                    Console.WriteLine(i + ". Name: '" + n.Name + "'");
                }
            }
            catch(NeoException ex)
            {
                Console.WriteLine(ex.ToString());
            }
            Console.ReadKey();
        }


        class MyNode
        {
            private string _name = "";

            public string Name
            {
                get
                {
                    return _name;
                }

                set
                {
                    _name = value;
                }
            }
        }
        public class MyRelationShip : Relationship, IRelationshipAllowingSourceNode<MyNode>, IRelationshipAllowingTargetNode<MyNode>
        {
            public static readonly string TypeKey = "MYRELATIONSHIP";

            public MyRelationShip(NodeReference targetNode)
                : base(targetNode)
            { }

            public override string RelationshipTypeKey
            {
                get { return TypeKey; }
            }
        }
    }
}