HotChocolate

A minimal GraphQL gateway in C#: one HotChocolate endpoint that merges a public REST API and a local SQLite database into a single User type, all in one Program.cs.

            GraphQL client  (browser IDE at http://localhost:5095/graphql)
                   │   query { user(id: 1) { id name email payments { amount date } } }
                   ▼
        ┌────────────────────────────────┐
        │  GettingStarted (ASP.NET Core) │
        │  HotChocolate  Query.GetUser   │
        └───────┬──────────────┬─────────┘
                │              │
   HttpClient   │              │  EF Core
                ▼              ▼
   jsonplaceholder.typicode.com    payments.db (SQLite)
   /users/{id}  -> name, email     Payments where UserId = id
                │              │
                └──── merged ──┘
                       ▼
                 one User object

This project is a self-hosted GraphQL server built with HotChocolate. It acts as a gateway that unifies data from a public REST API (JSONPlaceholder) and a local SQLite database (payments.db) behind one GraphQL endpoint.

Why

• See the gateway pattern end to end in a single Program.cs: one query, two back ends, one response.
• Learn how a HotChocolate resolver pulls services (IHttpClientFactory, a DbContext) straight into its parameters.
• Start from something that runs with dotnet run and seeds its own sample data.

Features

• A GraphQL API with a single endpoint, /graphql.
• Fetches user profiles from a remote API: https://jsonplaceholder.typicode.com/users/{id}.
• Fetches payment history from a local SQLite database through Entity Framework Core.
• Combines both sources into one User GraphQL type.
• Seeds two sample payments for user 1 on first start if the table is empty, and prints the table to the console.
• Built with ASP.NET Core, HotChocolate 13.5 and Entity Framework Core 7 with SQLite.

Quick start

Prerequisites: the .NET 7 SDK.

git clone https://github.com/mindattic/HotChocolate.git
cd HotChocolate/GettingStarted
dotnet run

Open http://localhost:5095/graphql in your browser (the http launch profile opens it for you). Paste this query and click Run:

query {
  user(id: 1) {
    id
    name
    email
    payments {
      amount
      date
    }
  }
}

The response carries the user's name and email from JSONPlaceholder and their payments from payments.db, in one JSON object.

How it works

The user(id) query is the Query.GetUserAsync resolver in Program.cs. It:

1. Calls the JSONPlaceholder API to get the user's name and email.
2. Queries payments.db for payment records with a matching UserId.
3. Merges both into one User and returns it. If the API returns nothing, the name is Unknown.

Schema:

Type	Fields
User	id, name, email, payments
Payment	paymentId, userId, amount, date

Sample data

Program.cs creates the database if it does not exist and, when the Payments table is empty, adds two payments for user 1 (100.00 and 150.00, dated 10 and 5 days before the first run).

GettingStarted/CreateDatabase.py rebuilds payments.db from scratch with the same two payments at fixed dates (2025-03-21 and 2025-03-26):

python CreateDatabase.py

Project layout

Path	What it is
GettingStarted/Program.cs	Host setup, GraphQL registration, the Query resolver, models and PaymentDbContext
GettingStarted/GettingStarted.csproj	.NET 7 web project with HotChocolate and EF Core SQLite packages
GettingStarted/payments.db	The sample SQLite database
GettingStarted/CreateDatabase.py	Rebuilds the sample database
GettingStarted/Properties/launchSettings.json	http profile on port 5095

Limitations

• This is a learning example, not a production gateway: there is no authentication, caching, batching (DataLoader) or error handling around the REST call.
• Projections, filtering and sorting are registered on the server, but the user field does not opt into them.
• The startup message prints http://localhost:5000/graphql, but the launch profile serves on port 5095; use 5095.
• The repository also contains committed bin, obj and .vs folders from a local build; they are not needed to run it.

Documentation

• HotChocolate documentation for the GraphQL server used here.

License

This repository has no LICENSE file; all rights are reserved.

Part of MindAttic — see more projects at github.com/mindattic.