Carpooling GraphQL Application

A .NET Core GraphQL application built with HotChocolate for a carpooling service.

Features

• GraphQL API with HotChocolate
• Entity Framework Core with SQL Server
• Real-time subscriptions for live updates
• Comprehensive data model for carpooling services
• Filtering, sorting, and projections support

Prerequisites

• .NET 8.0 SDK
• SQL Server (LocalDB or full instance)
• Visual Studio 2022 or VS Code

Database Setup

1. Create the database using the provided SQL script:

   • Open SQL/CarpoolingSchema.txt
   • Execute the script in SQL Server Management Studio or Azure Data Studio
   • Or use the Entity Framework migrations (see below)

2. Update connection string in appsettings.json if needed:

   {
     "ConnectionStrings": {
       "DefaultConnection": "Server=(LocalDB)\\MSSQLLocalDB;Database=CarpoolingDB;Trusted_Connection=True;MultipleActiveResultSets=true;"
     }
   }

Entity Framework Migrations

If you want to use EF migrations instead of the SQL script:

# Add initial migration
dotnet ef migrations add InitialCreate

# Update database
dotnet ef database update

Running the Application

1. Restore packages:

   dotnet restore

2. Run the application:

   dotnet run

3. Access the application:

   • GraphQL endpoint: https://localhost:7000/graphql
   • GraphQL Playground: https://localhost:7000/graphql-voyager
   • Swagger UI: https://localhost:7000/swagger

GraphQL Schema

Queries

• users - Get all users
• user(userId: Int!) - Get user by ID
• drivers - Get all drivers
• driver(driverId: Int!) - Get driver by ID
• riders - Get all riders
• rider(riderId: Int!) - Get rider by ID
• bookings - Get all bookings
• booking(bookingId: UUID!) - Get booking by ID
• packages - Get all packages
• package(packageId: Int!) - Get package by ID
• packageCategories - Get all package categories
• payments - Get all payments
• transactions - Get all transactions

Mutations

• createUser(input: CreateUserInput!) - Create a new user
• createDriver(input: CreateDriverInput!) - Create a new driver
• createRider(input: CreateRiderInput!) - Create a new rider
• createBooking(input: CreateBookingInput!) - Create a new booking
• createPackage(input: CreatePackageInput!) - Create a new package
• createPayment(input: CreatePaymentInput!) - Create a new payment
• updateBookingStatus(bookingId: UUID!, status: String!) - Update booking status

Subscriptions

• onBookingStatusChanged - Subscribe to booking status changes
• onDriverLocationUpdated - Subscribe to driver location updates
• onPaymentReceived - Subscribe to payment notifications
• onRideCompleted - Subscribe to ride completion events

Example GraphQL Queries

Get all users with their roles

query {
  users {
    userId
    firstName
    lastName
    email
    role {
      roleName
    }
  }
}

Create a new user

mutation {
  createUser(input: {
    firstName: "John"
    lastName: "Doe"
    email: "john.doe@example.com"
    passwordHash: "hashedpassword"
    phoneNumber: "+1234567890"
    roleId: 1
  }) {
    userId
    firstName
    lastName
    email
  }
}

Get booking with related data

query {
  booking(bookingId: "123e4567-e89b-12d3-a456-426614174000") {
    bookingId
    pickupLocation
    dropoffLocation
    bookingStatus
    requestedTime
    rider {
      user {
        firstName
        lastName
      }
    }
    driver {
      user {
        firstName
        lastName
      }
      vehicleType
      vehiclePlateNumber
    }
    package {
      packageName
      price
    }
  }
}

Project Structure

CarpoolingGraphQL/
├── Models/                 # Entity models
├── Data/                   # DbContext and data access
├── GraphQL/                # GraphQL types (Query, Mutation, Subscription)
├── SQL/                    # Database schema script
├── appsettings.json        # Configuration
├── Program.cs              # Application entry point
└── README.md               # This file

Technologies Used

• .NET 8.0 - Framework
• HotChocolate 13.7.0 - GraphQL server
• Entity Framework Core 8.0 - ORM
• SQL Server - Database
• ASP.NET Core - Web framework

Development

Adding New GraphQL Types

1. Create new model in Models/ folder
2. Add DbSet to CarpoolingDbContext
3. Add queries/mutations in GraphQL/Query.cs or GraphQL/Mutation.cs
4. Configure relationships in OnModelCreating method

Database Changes

1. Modify entity models
2. Create new migration: dotnet ef migrations add MigrationName
3. Update database: dotnet ef database update

Troubleshooting

Common Issues

1. Database connection failed

   • Verify SQL Server is running
   • Check connection string in appsettings.json
   • Ensure database exists

2. GraphQL schema errors

   • Check for missing using statements
   • Verify entity relationships are properly configured
   • Ensure all required packages are installed

3. Migration errors

   • Delete existing migrations folder
   • Drop and recreate database
   • Run dotnet ef database update again

License

This project is for educational and development purposes.