GraphQL with .NET: Hot Chocolate Library

Hot Chocolate is the premier GraphQL server for .NET. Unlike Rest APIs, GraphQL allows clients to ask for exactly what they need, solving over-fetching. Hot Chocolate 11 brings massive performance improvements and the “Banana Cake Pop” IDE.

Schema Definition (Code-First)

public class Query
{
    public IQueryable<Book> GetBooks([Service] ApplicationDbContext db) =>
        db.Books;
}

// Startup.cs
services
    .AddGraphQLServer()
    .AddQueryType<Query>()
    .AddProjections() // IQueryable to SQL translation!
    .AddFiltering()
    .AddSorting();

Handling Relationships (DataLoaders)

The “N+1 Problem” is the enemy of GraphQL. Use DataLoaders to batch requests.

public class Book
{
    public int AuthorId { get; set; }
    
    // Resolver
    public async Task<Author> GetAuthorAsync(
        [Service] AuthorDataLoader loader,
        CancellationToken ct)
    {
        return await loader.LoadAsync(AuthorId, ct);
    }
}

Key Takeaways

• Use **Projections** to let Hot Chocolate generate efficient SQL via EF Core.
• Use **DataLoaders** to prevent N+1 queries.
• Banana Cake Pop is a great tool for testing queries.