c# - EntityFramework 和级联删除

Question

我对级联删除有疑问。如果可能的话，我想使用它，但在某些情况下它对我不起作用。我已将我的 DbContext 设置为如下所示:

public class DatabaseContext : IdentityDbContext<User>
{

    // Define our tables
    public DbSet<Company> Companies { get; set; }
    public DbSet<Center> Centers { get; set; }
    public DbSet<Collection> Collections { get; set; }
    public DbSet<UserCenter> UserCenters { get; set; }
    public DbSet<Journal> Journal { get; set; }

    /// <summary>
    /// static constructor (only gets called once)
    /// </summary>
    static DatabaseContext()
    {

        // Create the database and insert our records
        Database.SetInitializer<DatabaseContext>(new DatabaseInitializer());
    }

    /// <summary>
    /// Default constructor
    /// </summary>
    public DatabaseContext()
        : base("DefaultConnection")
    {

        // Write our SQL to the debug window
        this.Database.Log = s => Debug.WriteLine(s);

        // Disable Lazy Loading
        base.Configuration.LazyLoadingEnabled = false;
    }

    // Public static method for OWIN
    public static DatabaseContext Create()
    {
        return new DatabaseContext();
    }

    /// <summary>
    /// Overrides the inherited OnModelCreated method.
    /// </summary>
    /// <param name="modelBuilder">The DbModelBuilder</param>
    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {

        // Change default table names for Identity Framework
        modelBuilder.Entity<IdentityRole>().ToTable("Roles");
        modelBuilder.Entity<IdentityUserRole>().ToTable("UserRoles");
        modelBuilder.Entity<IdentityUserClaim>().ToTable("UserClaims");
        modelBuilder.Entity<IdentityUserLogin>().ToTable("UserLogins");

        // Create mappings for Identity Framework
        modelBuilder.Entity<IdentityUserLogin>().HasKey(m => new { m.UserId, m.ProviderKey });
        modelBuilder.Entity<IdentityRole>().HasKey<string>(m => m.Id);
        modelBuilder.Entity<IdentityUserRole>().HasKey(m => new { m.RoleId, m.UserId });
        modelBuilder.Entity<User>().HasMany(m => m.Logins).WithRequired().HasForeignKey(m => m.UserId);
        modelBuilder.Entity<IdentityRole>().HasMany(m => m.Users).WithRequired().HasForeignKey(m => m.RoleId);

        // Create our mappings
        modelBuilder.Entity<UserCenter>().HasKey(m => new { m.UserId, m.CenterId });
        modelBuilder.Entity<Center>().HasRequired(m => m.Company).WithMany(m => m.Centers).HasForeignKey(m => m.CompanyId);
        modelBuilder.Entity<Center>().HasMany(m => m.Collections).WithRequired().HasForeignKey(m => m.CenterId);
        modelBuilder.Entity<Company>().HasMany(m => m.Members).WithOptional().HasForeignKey(m => m.CompanyId).WillCascadeOnDelete(false);

        // Archive relationships
        modelBuilder.Entity<User>().HasOptional(m => m.CreatedBy).WithMany().HasForeignKey(m => m.CreatedById).WillCascadeOnDelete(false);
        modelBuilder.Entity<User>().HasOptional(m => m.ModifiedBy).WithMany().HasForeignKey(m => m.ModifiedById).WillCascadeOnDelete(false);
        modelBuilder.Entity<Company>().HasRequired(m => m.CreatedBy).WithMany().HasForeignKey(m => m.CreatedById).WillCascadeOnDelete(false);
        modelBuilder.Entity<Company>().HasRequired(m => m.ModifiedBy).WithMany().HasForeignKey(m => m.ModifiedById).WillCascadeOnDelete(false);
        modelBuilder.Entity<Collection>().HasRequired(m => m.CreatedBy).WithMany().HasForeignKey(m => m.CreatedById).WillCascadeOnDelete(false);
        modelBuilder.Entity<Collection>().HasRequired(m => m.ModifiedBy).WithMany().HasForeignKey(m => m.ModifiedById).WillCascadeOnDelete(false);
        modelBuilder.Entity<Center>().HasRequired(m => m.CreatedBy).WithMany().HasForeignKey(m => m.CreatedById).WillCascadeOnDelete(false);
        modelBuilder.Entity<Center>().HasRequired(m => m.ModifiedBy).WithMany().HasForeignKey(m => m.ModifiedById).WillCascadeOnDelete(false);
        modelBuilder.Entity<Journal>().HasRequired(m => m.User).WithMany().HasForeignKey(m => m.UserId).WillCascadeOnDelete(false);
    }
}

如您所见，我有一些存档映射，我已从中禁用级联删除。这是设计使然，因为我不想删除一个项目，它会删除创建/修改它的用户:)

如果我删除一个 Center 并且它有一些 Collections，它会正常删除并且删除这些集合。如果我删除一个 User 并且他有一些 UserCenter 也会被删除，但是如果我尝试删除一个 Company (它有用户，用户有用户中心)它失败了，我得到一个异常:

exceptionMessage=The DELETE statement conflicted with the REFERENCE constraint "FK_dbo.Users_dbo.Companies_CompanyId". The conflict occurred in database "melanite", table "dbo.Users", column 'CompanyId'. The statement has been terminated.

我可以看到它在 User 的 CompanyId 字段中提示，所以我更改了这一行:

modelBuilder.Entity<Company>().HasMany(m => m.Members).WithOptional().HasForeignKey(m => m.CompanyId).WillCascadeOnDelete(false);

因为如果我删除一个用户，我不希望它删除用户所属的公司。但是，另一方面，如果我删除一个 Company 我确实希望它删除 Users...

有人知道如何解决我的问题吗？

Answer 1

只需配置您的 FK 以在级联中删除:

modelBuilder.Entity<Company>().HasMany(m => m.Members).WithOptional().HasForeignKey(m => m.CompanyId).WillCascadeOnDelete(true);

级联删除总是在一个方向上进行，从引用表(公司)到引用表(用户)，因此删除公司也会删除其用户，但删除用户不会对引用的公司做任何事情。