ASP.Net MVC 3 EF“在表上引入 FOREIGN KEY 约束可能会导致循环或多个级联路径”

Question

我正在创建一个 ASP.Net MVC 3 应用程序，但在尝试使用迁移更新我的数据库时遇到了外键约束问题。我正在使用 Code-First，我得到的错误是：

在表“CategoryItemValues”上引入 FOREIGN KEY 约束“FK_CategoryItemValues_CategoryProperties_CategoryPropertyId”可能会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。查看以前的错误。

这是我的课程：

public class Category
{
    public int Id { get; set; }
    [Display(Name = "Category Name")]
    public string CategoryName { get; set; }
    [Display(Name = "Display Name")]
    public string DisplayName { get; set; }
    [Display(Name = "Display Order")]
    public int DisplayOrder { get; set; }
    public bool IsTab { get; set; }
    public bool Active { get; set; }

    public virtual List<CategoryProperty> Properties { get; set; }
}

public class CategoryProperty
{
    public int Id { get; set; }
    public int CategoryId { get; set; }
    [Display(Name="Property Name")]
    public string PropertyName { get; set; }
    [Display(Name = "Display Order")]
    public int DisplayOrder { get; set; }

    public virtual Category Category { get; set; }
}

public class CategoryItem
{
    public int Id { get; set; }
    public int CategoryId { get; set; }

    public virtual Category Category { get; set; }
    public virtual List<CategoryItemValue> Values { get; set; }
}

public class CategoryItemValue
{
    public int Id { get; set; }
    public int CategoryItemId { get; set; }
    public int CategoryPropertyId { get; set; }
    public string Value { get; set; }

    public virtual CategoryItem Item { get; set; }
    public virtual CategoryProperty Property { get; set; }
}

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    // I know that the solution needs to go here!
}

似乎我需要为 CategoryItemValues 禁用 Cascade on Delete，但我不知道该怎么做。我知道我需要这样做：

modelBuilder.Entity<...>() .HasRequired(...) 。与许多（...） .HasForeignKey(...) .WillCascadeOnDelete(false);

但我不能完全正确。

Answer 1

这应该可行...

public class Category
{
    public int Id { get; set; }
    public string CategoryName { get; set; }
    public string DisplayName { get; set; }
    public int DisplayOrder { get; set; }
    public bool IsTab { get; set; }
    public bool Active { get; set; }
    public virtual List<CategoryProperty> Properties { get; set; }
    public virtual List<CategoryItem> Items { get; set; }
}
public class CategoryProperty
{
    public int Id { get; set; }
    public int CategoryId { get; set; }
    public string PropertyName { get; set; }
    public int DisplayOrder { get; set; }
    public virtual Category Category { get; set; }
    public virtual List<CategoryItemValue> Values { get; set; }
}
public class CategoryItem
{
    public int Id { get; set; }
    public int CategoryId { get; set; }
    public virtual Category Category { get; set; }
    public virtual List<CategoryItemValue> Values { get; set; }
}
public class CategoryItemValue
{
    public int Id { get; set; }
    public int CategoryItemId { get; set; }
    public int CategoryPropertyId { get; set; }
    public string Value { get; set; }
    public virtual CategoryItem Item { get; set; }
    public virtual CategoryProperty Property { get; set; }
}

...以及“要点”...

modelBuilder.Entity<CategoryProperty>()
    .HasKey(i => i.Id);

modelBuilder.Entity<CategoryProperty>()
    .HasRequired(i => i.Category)
    .WithMany(u => u.Properties)
    .HasForeignKey(i => i.CategoryId)
    .WillCascadeOnDelete(false);

modelBuilder.Entity<CategoryItem>()
    .HasKey(i => i.Id);

modelBuilder.Entity<CategoryItem>()
    .HasRequired(i => i.Category)
    .WithMany(u => u.Items)
    .HasForeignKey(i => i.CategoryId)
    .WillCascadeOnDelete(false);

modelBuilder.Entity<CategoryItemValue>()
    .HasKey(i => i.Id);

modelBuilder.Entity<CategoryItemValue>()
    .HasRequired(i => i.Item)
    .WithMany(u => u.Values)
    .HasForeignKey(i => i.CategoryItemId)
    .WillCascadeOnDelete(false);

modelBuilder.Entity<CategoryItemValue>()
    .HasRequired(i => i.Property)
    .WithMany(u => u.Values)
    .HasForeignKey(i => i.CategoryPropertyId)
    .WillCascadeOnDelete(false);