Using .NET to connect to a Neptune DB instance

If you can, always use the latest version of the Apache TinkerPop .NET Gremlin client, Gremlin.Net, that your engine version supports. Newer versions contain numerous bug fixes that improve the stability, performance and usability of the client. The Gremlin.Net version to use will typically align with the TinkerPop versions described in the table for the Java Gremlin client.

The following section contains a code example written in C# that connects to a Neptune DB instance and performs a Gremlin traversal.

Connections to Amazon Neptune must be from an Amazon EC2 instance in the same virtual private cloud (VPC) as your Neptune DB instance. This sample code was tested on an Amazon EC2 instance running Ubuntu.

Before you begin, do the following:

• Install .NET on the Amazon EC2 instance. To get instructions for installing .NET on multiple operating systems, including Windows, Linux, and macOS, see Get Started with .NET.

• Install Gremlin.NET by running dotnet add package gremlin.net for your package. For more information, see Gremlin.NET in the TinkerPop documentation.

To connect to Neptune using Gremlin.NET

1. Create a new .NET project.

   dotnet new console -o gremlinExample

2. Change directories into the new project directory.

   cd gremlinExample

3. Copy the following into the Program.cs file. Replace your-neptune-endpoint with the address of your Neptune DB instance.

   For information about finding the address of your Neptune DB instance, see the Connecting to Amazon Neptune Endpoints section.

   using System;
   using System.Threading.Tasks;
   using System.Collections.Generic;
   using Gremlin.Net;
   using Gremlin.Net.Driver;
   using Gremlin.Net.Driver.Remote;
   using Gremlin.Net.Structure;
   using static Gremlin.Net.Process.Traversal.AnonymousTraversalSource;
   namespace gremlinExample
   {
     class Program
     {
       static void Main(string[] args)
       {
         try
         {
           var endpoint = "your-neptune-endpoint";
           // This uses the default Neptune and Gremlin port, 8182
           var gremlinServer = new GremlinServer(endpoint, 8182, enableSsl: true );
           var gremlinClient = new GremlinClient(gremlinServer);
           var remoteConnection = new DriverRemoteConnection(gremlinClient, "g");
           var g = Traversal().WithRemote(remoteConnection);
           g.AddV("Person").Property("Name", "Justin").Iterate();
           g.AddV("Custom Label").Property("name", "Custom id vertex 1").Iterate();
           g.AddV("Custom Label").Property("name", "Custom id vertex 2").Iterate();
           var output = g.V().Limit<Vertex>(3).ToList();
           foreach(var item in output) {
               Console.WriteLine(item);
           }
         }
         catch (Exception e)
         {
             Console.WriteLine("{0}", e);
         }
       }
     }
   }

4. Enter the following command to run the sample:

   dotnet run

   The Gremlin query at the end of this example returns the count of a single vertex for testing purposes. It is then printed to the console.

   Note

   The final part of the Gremlin query, Next(), is required to submit the traversal to the server for evaluation. If you don't include that method or another equivalent method, the query is not submitted to the Neptune DB instance.

   The following methods submit the query to the Neptune DB instance:

   • ToList()

   • ToSet()

   • Next()

   • NextTraverser()

   • Iterate()

   Use Next() if you need the query results to be serialized and returned, or Iterate() if you don't.

   The preceding example returns a list by using the g.V().Limit(3).ToList() traversal. To query for something else, replace it with another Gremlin traversal with one of the appropriate ending methods.