EntityFrameworkCore 单表树状结构配置

数据结构

public class TreeNode
{
    [Key]
    public long Id { get; set; }
    public string NodeName { get; set; }
    public long? ParentId { get; set; }
    public virtual TreeNode Parent { get; set; }
    public virtual ICollection<TreeNode> Children { get; set; }

}

配置

//单表树状结构
modelBuilder.Entity<TreeNode>()
    //主语this，拥有Children
    .HasMany(x => x.Children)
    //主语Children，每个Child拥有一个Parent
    .WithOne(x => x.Parent)
    //主语Children，每个Child的外键是ParentId
    .HasForeignKey(x => x.ParentId)
    //这里必须是非强制关联，否则报错：Specify ON DELETE NO ACTION or ON UPDATE NO ACTION, or modify other FOREIGN KEY constraints.
    .OnDelete(DeleteBehavior.ClientSetNull);

数据查询需要使用延迟加载

protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    => optionsBuilder
        .UseLazyLoadingProxies()
        .UseSqlServer(myConnectionString);

或者

    .AddDbContext<BloggingContext>(
        b => b.UseLazyLoadingProxies()
              .UseSqlServer(myConnectionString));

参考资料：https://docs.microsoft.com/zh-cn/ef/core/querying/related-data#lazy-loading

示例代码

https://github.com/zLulus/NotePractice/blob/dev3/Website/DotNetCore/CoreWebsite.EntityFramework/WebsiteDbContext.cs