OnDelete(DeleteBehavior.Cascade) 可能导致循环或多个级联路径

Question

我有一个产品 table 和一个类别 table。我试图在产品和类别之间建立多对多关系。所以我有一个 Table 叫做：ProductCategories - 我遵循了官方文档：

https://docs.microsoft.com/en-us/ef/core/modeling/relationships?tabs=fluent-api%2Cfluent-api-composite-key%2Csimple-key

public class ProductCategory
{
    public Guid ProductId { get; set; }
    public Product  Product { get; set; }
    
    public Guid CategoryId { get; set; }
    public Category  Category { get; set; }
}

 public class Product
{
     public Product()
    {
        ProductFiles = new Collection<ProductFiles>();
    }
    
    public Company Company { get; set; }
    public Guid CompanyId { get; set; }
    
    public string Name { get; set; }
    public string Description { get; set; }
    public decimal SalePrice { get; set; }
    public decimal? CostPrice { get; set; }
    public int VatPercentage { get; set; } = 25;

    public ICollection<ProductFiles> ProductFiles { get; set; }
    
    public ICollection<ProductCategory> Categories { get; set; }
}

public class Category
{
   public string Title { get; set; }
    
    public Guid CompanyId { get; set; }
    public Company Company { get; set; }
    public Guid? ParentCategoryId { get; set; }
    public virtual ICollection<Category> SubCategories { get; set; }
    public virtual Category ParentCategory { get; set; }
    
    public bool Visible { get; set; } = true;

    public int SortOrder { get; set; } = 1;
    
    public ICollection<ProductCategory> Products { get; set; }
}

并且在模型构建器中我指定了关系

        builder.Entity<Company>()
            .HasMany(c => c.Products)
            .WithOne(e => e.Company);
        

        builder.Entity<Product>()
            .Property(p => p.CostPrice)
            .HasColumnType("decimal(18,2)"); 
        
        builder.Entity<Product>()
            .Property(p => p.SalePrice)
            .HasColumnType("decimal(18,2)");

        builder.Entity<Category>()
            .HasMany<Category>(c => c.SubCategories)
            .WithOne(c => c.ParentCategory)
            .HasForeignKey(c => c.ParentCategoryId)
            .OnDelete(DeleteBehavior.Restrict);
        
        builder.Entity<Company>()
            .HasMany<Category>(p => p.Categories)
            .WithOne(p => p.Company)
            .HasForeignKey(p => p.CompanyId).OnDelete(DeleteBehavior.Cascade);

builder.Entity() .HasKey(x => new {x.ProductId, x.CategoryId});

        builder.Entity<ProductCategory>()
            .HasOne<Product>(pc => pc.Product)
            .WithMany(p => p.Categories)
            .HasForeignKey(p => p.ProductId);

        builder.Entity<ProductCategory>()
            .HasOne<Category>(p => p.Category)
            .WithMany(p => p.Products)
            .HasForeignKey(p => p.CategoryId);

问题是当我尝试更新数据库时出现错误“可能导致循环或多个级联路径。指定 ON DELETE NO ACTION 或 ON UPDATE NO ACTION，或修改其他 FOREIGN KEY 约束。 无法创建约束或索引。"

我想要的是当系统中有人删除一个category/product时，它应该删除ProductCategories中的记录 - 当我尝试添加onDelete时没有动作，那么我无法删除category/product 在 ProductsCategory table.

中没有它们的关系

关于如何最好地解决这个问题有什么建议吗？

Answer 1

公司配置为级联删除类别和产品。那是“多级联路径”，是不允许的。将所有 FK 配置放在一起，可以更轻松地查看哪些关系可以级联。例如

    builder.Entity<Company>()
        .HasMany(c => c.Products)
        .WithOne(e => e.Company)
        .OnDelete(DeleteBehavior.Cascade);

    builder.Entity<Company>()
       .HasMany(p => p.Categories)
       .WithOne(p => p.Company)
       .HasForeignKey(p => p.CompanyId)
       .OnDelete(DeleteBehavior.Restrict);

    builder.Entity<Category>()
        .HasMany(c => c.SubCategories)
        .WithOne(c => c.ParentCategory)
        .HasForeignKey(c => c.ParentCategoryId)
        .OnDelete(DeleteBehavior.Restrict);

    builder.Entity<ProductCategory>()
        .HasOne(pc => pc.Product)
        .WithMany(p => p.Categories)
        .HasForeignKey(p => p.ProductId)
        .OnDelete(DeleteBehavior.Cascade);

    builder.Entity<ProductCategory>()
        .HasOne(p => p.Category)
        .WithMany(p => p.Products)
        .HasForeignKey(p => p.CategoryId)
        .OnDelete(DeleteBehavior.Cascade);