I'm building a Web API using .NET 6 and Entity Framework Core to connect to a SQL Server database. The basic stuff looks like it's working, but I cannot make the many-to-many relationships in my models work.

Considering the following 3 tables in the database:

**Products**:

[![enter image description here](https://i.stack.imgur.com/tXNJZ.png)](https://i.stack.imgur.com/tXNJZ.png)

**Categories**:

[![enter image description here](https://i.stack.imgur.com/SDmkf.png)](https://i.stack.imgur.com/SDmkf.png)

**CategoryProduct**:

[![enter image description here](https://i.stack.imgur.com/mPe8J.png)](https://i.stack.imgur.com/mPe8J.png)

I have created 3 models corresponding to these tables as follows:

```
public class Product
{
    [Key]
    public int Id { get; set; }             = 0;
    public string Name { get; set; }        = string.Empty;
    public string Description { get; set; } = string.Empty;
    public string Label { get; set; }       = string.Empty;
    public int Sativa { get; set; }         = 0;
    public int Indica { get; set; }         = 0;

    public ICollection<CategoryProduct> Categories { get; set; } = new HashSet<CategoryProduct>();
}

public class Category
{
    [Key]
    public int Id { get; set; }      = 0;
    public string Name { get; set; } = string.Empty;
    public int Order { get; set; }   = 0;

    public ICollection<CategoryProduct> Products { get; set; } = new HashSet<CategoryProduct>();
}

public class CategoryProduct
{
    public int CategoryId { get; set; }     = 0;
    public Category? Category { get; set; } = null;
    public int ProductId { get; set; }      = 0;
    public Product? Product { get; set; }   = null;
}

```

I have created the following `DbContext` class to communicate with the database:

```
public class CoffeeshopContext : DbContext
{
    public DbSet<Shop>? Shops { get; set; }                        = null;
    public DbSet<Category>? Categories { get; set; }               = null;
    public DbSet<Product>? Products { get; set; }                  = null;
    public DbSet<Price>? Prices { get; set; }                      = null;
    public DbSet<CategoryProduct>? ProductCategories { get; set; } = null;

    private readonly IConfiguration _configuration;

    public CoffeeshopContext(DbContextOptions<CoffeeshopContext> options, IConfiguration configuration) : base(options)
    {
        _configuration = configuration;
    }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<CategoryProduct>().HasKey(x => new { x.CategoryId, x.ProductId });
        modelBuilder.Entity<CategoryProduct>().HasOne(x => x.Product)
                                              .WithMany(x => x.Categories)
                                              .HasForeignKey(x => x.ProductId);
        modelBuilder.Entity<CategoryProduct>().HasOne(x => x.Category)
                                              .WithMany(x => x.Products)
                                              .HasForeignKey(x => x.CategoryId);
        base.OnModelCreating(modelBuilder);
    }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        if (!optionsBuilder.IsConfigured)
            optionsBuilder.UseSqlServer(_configuration.GetConnectionString(nameof(CoffeeshopContext)));
    }
}

```

When I run the project using swagger, I get the following results when calling and endpoint which retrieves the Products:

```
[
  {
    "id": 3,
    "name": "Ice Cream Bean",
    "description": "Well balanced hybrid with a mood boosting euphoric high and body relaxation. Diesel and citrus aroma with creamy fruity undertones.",
    "label": "CALI STRAIN",
    "sativa": 50,
    "indica": 50,
    "categories": []
  },
  {
    "id": 4,
    "name": "Blue Cheese",
    "description": "Deep relaxing, calming and pain relief. Berry, blue cheese aroma and a creamy taste.",
    "label": "CLASSIC STRAIN",
    "sativa": 20,
    "indica": 80,
    "categories": []
  }
]

```

So, the endpoint is working and retrieving products from the database.

However, for some reason it does not make the relationship to categories (and yes, I am sure there are records in the `ProductCategory` table to define the relationship between products and categories). I am sure I am missing something, but I don't see what it is I'm missing. Can someone perhaps point me in the right direction on how to make this work?