Neo4j

Description

Neo4j can be used as the backing implementation for Flex graph operations. Your application code should depend on IFlexGraphStore, while Flex provides the Neo4j implementation and wiring.

Important concepts

• IFlexGraphStore is the contract: your app uses a shared graph abstraction rather than Neo4j driver APIs.

• Nodes are models: graph operations typically read/write node models (domain models) through the store.

• Generated flow: generated handlers/queries use cmd.Dto.GetAppContext() / params.GetAppContext() and then call IFlexGraphStore.

Configuration in DI

Add the provider in your DI composition root (commonly in EndPoints/...CommonConfigs/OtherApplicationServicesConfig.cs).

public static class OtherApplicationServicesConfig
{
	public static IServiceCollection AddOtherApplicationServices(
		this IServiceCollection services,
		IConfiguration configuration)
	{
		// Registers Neo4j as the IFlexGraphStore bridge.
		// Flex auto-wires generated Queries/Handlers that use IFlexGraphStore.
		services.AddFlexNeo4jGraphStore(configuration);

		return services;
	}
}

appsettings.json

Configuration is read from FlexBase:DataStores:Graph:Neo4j.

{
  "FlexBase": {
	"DataStores": {
	  "Graph": {
		"Neo4j": {
		  "Uri": "bolt://localhost:7687",
		  "Username": "neo4j",
		  "Password": "...",
		  "Database": "neo4j"
		}
	  }
	}
  }
}

Examples (template-based)

These examples mirror the generated Query and PostBusHandler templates. You do not register these types manually—Flex discovers and wires generated Queries/Handlers automatically.

Create node (PostBusHandler)

using Microsoft.Extensions.Logging;
using Sumeru.Flex;
using System;
using System.Threading.Tasks;

namespace {YourApplication}.Handlers.Graph;

public partial class CreateUserNodeHandler : IAmFlexCommandHandler<CreateUserNodeCommand>
{
	protected string EventCondition = "";

	protected readonly ILogger<CreateUserNodeHandler> _logger;
	protected readonly IFlexHost _flexHost;
	protected readonly IFlexGraphStore _graphStore;

	public CreateUserNodeHandler(ILogger<CreateUserNodeHandler> logger, IFlexHost flexHost, IFlexGraphStore graphStore)
	{
		_logger = logger;
		_flexHost = flexHost;
		_graphStore = graphStore;
	}

	public virtual async Task Execute(CreateUserNodeCommand cmd, IFlexServiceBusContext serviceBusContext)
	{
		_logger.LogDebug("Starting Create Node for {EntityType}", nameof(UserNodeModel));

		var appContext = cmd.Dto.GetAppContext(); // do not remove this line

		var model = _flexHost.GetDomainModel<UserNodeModel>().Create(cmd);
		await _graphStore.CreateNodeAsync(model);

		// Example:
		// EventCondition = CreateUserNodeEvents.CONDITION_ONSUCCESS;
		await this.Fire(EventCondition, serviceBusContext);
	}
}

public class CreateUserNodeCommand : FlexCommandBridge<CreateUserNodeDto> { }

public class CreateUserNodeDto : DtoBridge
{
	public Guid Id { get; set; }
	public string UserName { get; set; }
}

public class UserNodeModel : FlexDomainModelBridge
{
	public Guid Id { get; set; }
	public string UserName { get; set; }
}

Get node by ID (Query)

using Microsoft.Extensions.Logging;
using Sumeru.Flex;
using System;
using System.Threading.Tasks;

namespace {YourApplication}.Queries.Graph;

public class GetUserNodeByIdQuery : FlexiQueryBridgeAsync<UserNodeDto>
{
	protected readonly ILogger<GetUserNodeByIdQuery> _logger;
	protected readonly IFlexHost _flexHost;
	protected readonly IFlexGraphStore _graphStore;
	protected GetUserNodeByIdParams _params;

	public GetUserNodeByIdQuery(ILogger<GetUserNodeByIdQuery> logger, IFlexHost flexHost, IFlexGraphStore graphStore)
	{
		_logger = logger;
		_flexHost = flexHost;
		_graphStore = graphStore;
	}

	public virtual GetUserNodeByIdQuery AssignParameters(GetUserNodeByIdParams @params)
	{
		_params = @params;
		return this;
	}

	public virtual async Task<UserNodeDto?> Fetch()
	{
		var appContext = _params.GetAppContext();

		var node = await _graphStore.GetNodeByIdAsync<UserNodeModel>(_params.Id);
		if (node == null) return default;

		return new UserNodeDto { Id = node.Id, UserName = node.UserName };
	}
}

public class GetUserNodeByIdParams : DtoBridge
{
	public Guid Id { get; set; }
}

public class UserNodeDto : DtoBridge
{
	public Guid Id { get; set; }
	public string UserName { get; set; }
}

Library-specific considerations

• Secrets: store Neo4j passwords in a secret manager and inject via configuration.

• Connection URI: use bolt+s:// (or your cluster’s required scheme) when connecting over TLS.