与实体框架核心和.net核心3.1的自引用连接

public class Category
{
    public int CategoryId { get; set; }
    public string Name { get; set; }
    public int? ParentCategoryId { get; set; }
    public Category ParentCategory { get; set; }
    public ICollection<Category> ChildCategories { get; set; }
}

public class MyDbContext : DbContext
{
    public DbSet<Category> Categories { get; set; }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        optionsBuilder.UseSqlServer("connectionString");
    }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Category>()
            .HasOne(c => c.ParentCategory)
            .WithMany(c => c.ChildCategories)
            .HasForeignKey(c => c.ParentCategoryId);
    }
}

// 使用自引用连接
using (var context = new MyDbContext())
{
    var parentCategory = new Category { Name = "Parent Category" };
    var childCategory = new Category { Name = "Child Category", ParentCategory = parentCategory };

    context.Categories.Add(parentCategory);
    context.Categories.Add(childCategory);
    context.SaveChanges();
}