Graph support

ISession has dedicated methods to execute graph queries:

using Cassandra.DataStax.Graph;

session.ExecuteGraph("system.createGraph('demo').ifNotExist().build()");

GraphStatement s1 = new SimpleGraphStatement("g.addV(label, 'test_vertex')").SetGraphName("demo");
session.ExecuteGraph(s1);

GraphStatement s2 = new SimpleGraphStatement("g.V()").SetGraphName("demo");
GraphResultSet rs = session.ExecuteGraph(s2);

GraphResultSet is a sequence of GraphNode elements. Each item can be converted to the expected type.

IVertex vertex = rs.First().To<IVertex>();
Console.WriteLine(vertex.Label);

Additionally, you can apply the conversion to all the sequence by using GraphResultSet.To<T>() method:

foreach (IVertex vertex in rs.To<IVertex>())
{
    Console.WriteLine(vertex.Label);
}

Graph options

You can set default graph options when initializing the cluster. They will be used for all graph statements. For example, to avoid repeating SetGraphName("demo") on each statement:

ICluster cluster = Cluster.Builder()
    .AddContactPoint("127.0.0.1")
    .WithGraphOptions(new GraphOptions().SetName("demo"))
    .Build();

If an option is set manually on a GraphStatement, it always takes precedence; otherwise the default option is used. This might be a problem if a default graph name is set, but you explicitly want to execute a statement targeting system, for which no graph name must be set. In that situation, use GraphStatement.SetSystemQuery():

GraphStatement s = new SimpleGraphStatement("system.createGraph('demo').ifNotExist().build()")
    .SetSystemQuery();
session.ExecuteGraph(s);

Asynchronous query execution

Graph statements can also be executed without blocking the calling thread using ExecuteGraphAsync() method.

GraphResultSet rs = await session.ExecuteGraphAsync(new SimpleGraphStatement("g.V()"));

Handling results

Graph queries return a GraphResultSet, which is a sequence of GraphNode elements:

GraphResultSet rs = session.ExecuteGraph(new SimpleGraphStatement("g.V()"));

// Iterating as IGraphNode
foreach (IGraphNode r in rs)
{
    Console.WriteLine(r);
}

IGraphNode represents a response item returned by the server. Each item can be converted to the expected type:

GraphResultSet rs = session.ExecuteGraph(new SimpleGraphStatement("g.V()"));
IVertex vertex = rs.First().To<IVertex>();
Console.WriteLine(vertex.Label);

Additionally, you can apply the conversion to all the sequence by using GraphResultSet.To<T>() method:

foreach (IVertex vertex in rs.To<IVertex>())
{
    Console.WriteLine(vertex.Label);
}

GraphNode provides implicit conversion operators to string, int, long and others in order to improve code readability, allowing the following C# syntax:

var rs = session.ExecuteGraph(new SimpleGraphStatement("g.V().has('name', 'marko').values('location')"));
foreach (string location in rs)
{
    Console.WriteLine(location);
}

GraphNode inherits from DynamicObject, allowing you to consume it using the dynamic keyword and/or as a dictionary.

dynamic r = session.ExecuteGraph(new SimpleGraphStatement("g.V()")).First();

You can get the GraphNode properties using the GetProperty() method from the element:

var vertex = session.ExecuteGraph(new SimpleGraphStatement("g.V()")).First().To<IVertex>();
// Assuming that vertex with properties: name:string, and age:int
Console.WriteLine(vertex.GetProperty("name").Value.ToString());
Console.WriteLine(vertex.GetProperty("age").Value.ToInt32());

Parameters

Graph query parameters are always named. Parameter bindings are passed as an anonymous type or as a IDictionary<string, object> alongside the query:

session.ExecuteGraph("g.addV(label, vertexLabel)", new { vertexLabel = "test_vertex_2" });

Note that, unlike in CQL, Gremlin placeholders are not prefixed with “:”.

Prepared statements

Prepared graph statements are not supported by DSE Graph.