c# - EF代码优先，不能删除外键关系

Question

这里显示了两个模型:

public class Application
{
  public string Name { get; set; }
  public virtual ICollection<ApplicationTransaction> ApplicationTransactions { get; set; }
}

和

public class ApplicationTransaction
{
  public long ApplicationId { get; set; }
  public virtual Application Application { get; set; }
}

我尝试使用以下代码删除 Application 的所有 ApplicationTransaction:

var app = _repository.Get<Application>(i => i.Id == 1);
app.ApplicationTransactions.Clear();
Context.SaveChanges();

但是当上下文去保存更改时，发生错误:

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.

Answer 1

我遇到了完全相同的问题，这是解决方案:

技巧:在设置父子关系时，您必须在子对象上创建一个“复合”键。这样，当您告诉 Parent 删除其 1 个或所有子项时，相关记录实际上将从数据库中删除。

使用 Fluent API 配置组合键:

modelBuilder.Entity<Child>.HasKey(t => new { t.ParentId, t.ChildId });

然后，删除相关的 child :

var parent = _context.Parents.SingleOrDefault(p => p.ParentId == parentId);

var childToRemove = parent.Children.First(); // Change the logic 
parent.Children.Remove(childToRemove);

// or, you can delete all children 
// parent.Children.Clear();

_context.SaveChanges();

完成!