MVC 实体框架 WillCascadeOnDelete 不起作用

Question

我正在做一个MVC Entity Framework 6 DataBase First应用程序。

我有两张桌子.. Groups 和MemberGroups，具有一对多的关系。

Foreign Key can not be Null

当我将数据库添加到我的应用程序时。.Edmx是用Context.cs文件生成的

 public partial class PortalEntities : DbContext
    {
        public VIvaVoceEntities()
            : base("name=PortalEntities")
        {
        }
    
        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
           throw new UnintentionalCodeFirstException();
        }
          public virtual DbSet<GroupMembers> GroupMembers { get; set; }
          
         public virtual DbSet<Groups> Groups { get; set; }
}

在.tt文件夹下，为每个表生成了class。

 public partial class Groups
 {
     public long Group_id { get; set; }
     public string Name { get; set; }
     public virtual ICollection<GroupMembers> GroupMembers { get; set; }
  }
          
  public partial class GroupMembers
  {
      public long MemberGroup_ID { get; set; }
      public long Group_id { get; set; }
   }

我正在尝试做一个Delete on cascade...删除组时，我想删除该组中的所有成员。因此，在OnModelCreating Context.cs文件中，我添加了我找到的所有内容，以便在级联中删除，但没有任何效果。

这是我到目前为止尝试过的。

   modelBuilder.Entity<Groups>()
             .HasMany(e => e.GroupMembers)
            .WithRequired(e => e.Groups)
            .WillCascadeOnDelete(true);
 ---------------------------------           
            
 modelBuilder.Entity<Groups>()
    .HasOptional(x => x.GroupMembers)
    .WithOptionalDependent()
    .WillCascadeOnDelete(true);            
 
 ---------------------------------
   
modelBuilder.Entity<Groups>().HasMany(i => i.GroupMembers)
            .WithOptional(i => i.Groups)
            .HasForeignKey(i => i.Group_id)
            .WillCascadeOnDelete(true);    
 ---------------------------------
            
modelBuilder.Entity<Groups>()
            .HasRequired(e => e.GroupMembers)
            .WithMany()
            .HasForeignKey(e => e.Group_id )
            .WillCascadeOnDelete(true);            

这是我用来删除它的代码。

  var master = _db.Set<Groups>().Include(m => m.GroupMembers).SingleOrDefault(m => m.Group_id == 2);
            _db.Set<Groups>().Remove(master);
            _db.SaveChanges();

我有以下错误...

"The operation failed: The relationship could not be changed because one or more of the foreign-key properties is non-nullable. When a change is made to a relationship, the related foreign-key property is set to a null value. If the foreign-key does not support null values, a new relationship must be defined, the foreign-key property must be assigned another non-null value, or the unrelated object must be deleted."

似乎它没有尝试删除子记录。它正在尝试使用空更新

正确的方法是什么。？

Answer 1

我用这段代码解决了。它不是我想要的级联，但这是我找到的最好的方法。

 public void Delete(long Group_id)
{
      Groups group = _db.Set<Groups>().Include(m => m.GroupMembers).SingleOrDefault(m => m.Group_id == Group_id);
      _db.GroupMembers.RemoveRange(group.GroupMembers);
      _db.SaveChanges();
      _db.Entry(group).State = System.Data.Entity.EntityState.Deleted;
      _db.SaveChanges();
   }