Apache AGE is an open-source extension for PostgreSQL which provides it with the capabilities of a graph database.
Here's a simple example to get you started:
using ApacheAGE;
var connectionString = "Host=server;Port=5432;Username=user;Password=pass;Database=sample1";
// Create a client.
var clientBuilder = new AgeClientBuilder(connectionString);
await using var client = clientBuilder.Build();
await client.OpenConnectionAsync();
// Create a graph and add vertices.
await client.CreateGraphAsync("graph1")
await client.ExecuteCypherAsync("graph1", "CREATE (:Person {age: 23}), (:Person {age:78})");
await using var reader = await client.ExecuteQueryAsync(
@"SELECT * FROM cypher('graph1', $$
MATCH (n:Person)
RETURN n
$$) AS (persons agtype);");
// Read the result row by row.
while(await reader.ReadAsync())
{
var agtypeResult = reader.GetValue(0);
Vertex person = agtypeResult.GetVertex();
// Do something with vertex.
}