I'm trying to create a many-to-many relationship in C# using the code first approach. In the real world, a product can have many categories and a category can have many products. So this is what I've come up with:
Product.cs:
public class Product
{
public int Id { get; set; }
public string Name { get; set; }
public virtual ICollection<Category> Categories { get; set; }
}
Category.cs:
public class Category
{
public Category(CategoryEnum @enum)
{
Id = (int)@enum;
Name = @enum.ToString();
}
public Category() { }
[Key, DatabaseGenerated(DatabaseGeneratedOption.None)]
public int Id { get; set; }
public string Name { get; set; }
public virtual ICollection<Product> Products { get; set; }
public static implicit operator Category(CategoryEnum @enum) => new Category(@enum);
public static implicit operator CategoryEnum(Category category) => (CategoryEnum)category.Id;
}
The Category
maps to an Enum
which looks like:
public enum CategoryEnum
{
Electronics = 1,
Gardening = 2
}
Finally, the DbContext
looks like so:
public class ProductDbContext : DbContext
{
public DbSet<Entities.Product> Products { get; set; }
public DbSet<Entities.Category> Categories { get; set; }
public ProductDbContext(DbContextOptions<ProductDbContext> options)
: base(options)
{ }
protected override void OnModelCreating(ModelBuilder builder)
{
base.OnModelCreating(builder);
}
}
When running migrations I get this result:
It's called name the columns like CategoriesId
and ProductsId
is there a way to change the name of these columns?
Have a go with this:
protected override void OnModelCreating(ModelBuilder builder)
{
base.OnModelCreating(builder);
builder
.Entity<Product>()
.HasMany(p => p.Categories)
.WithMany(p => p.Products)
.UsingEntity<Dictionary<string, object>>("ProductCategory",
right => right.HasOne<Category>()
.WithMany()
.HasForeignKey("CategoryId")
.HasConstraintName("FK_ProductCategory_CategoryId__Category_Id")
.OnDelete(DeleteBehavior.Cascade),
left => left.HasOne<Product>()
.WithMany()
.HasForeignKey("ProductId")
.HasConstraintName("FK_ProductCategory_ProductId__Product_Id")
.OnDelete(DeleteBehavior.Cascade)
);
}
It works:
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