How do I use Neo4jClient to get a Neo4j relation by its ID?

Question

I can create a relation and I have its RelationshipReference. But how do I get the rest of the relationship with payload and all?

With a Node I can just client.Get(nodeid) but AFAIK there is nothing similar for relations.

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Is Gremlin the way to go? If so - could someone give me a hint as I am still trial-and-horroring on how to do it through Neo4jClient.

Answer 1

You could use an extension method for the IGraphClient itself:

public static class GraphClientExtensions
{
    public static RelationshipInstance<T> GetRelationship<T>(this IGraphClient graphClient, RelationshipReference relationshipReference) where T : Relationship, new()
    {
        if(graphClient == null)
            throw new ArgumentNullException("graphClient");
        if(relationshipReference == null)
            throw new ArgumentNullException("relationshipReference");

        var rels = graphClient.ExecuteGetAllRelationshipsGremlin<T>(string.Format("g.e({0}).outV.outE", relationshipReference.Id), null);
        return rels.SingleOrDefault(r => r.Reference == relationshipReference);
    }
}

usage: (IsFriendOf is a Relationship derived class, Data just a POCO)

var d1 = new Data{Name = "A"};
var d2 = new Data{Name = "B"};

var d1Ref = graphClient.Create(d1);
var d2Ref = graphClient.Create(d2);
var rel = new IsFriendOf(d2Ref) { Direction = RelationshipDirection.Outgoing };
var relRef = graphClient.CreateRelationship(d1Ref, rel);

//USAGE HERE
var relBack = graphClient.GetRelationship<IsFriendOf>(relRef);

It's not ideal, but it does make your code a bit easier to read. (Plus you don't need to know the nodes, just the relationship reference)