Delete语句与引用约束冲突 [英] Delete statement conflicts with Reference constraint

问题描述

我认为这是一个非常简单的答案。我是实体框架的新手，正在创建一个由 Contacts 和 Groups 作为对象/实体的测试应用程序。

这是我删除组的代码：

 私人无效button_DeleteGroup_Click（对象发送者，EventArgs e）
 {
 var _selectedGroup = dataGridView_Groups.SelectedRows [0] .DataBoundItem as Group; 
 
试试
 {
 cgContext.Groups.Remove（_selectedGroup）; 
 cgContext.SaveChanges（）; 
 
 PopulateGroupGrid（）; 
 MessageBox.Show（已成功从数据库中删除组！）; 
} 
 catch（Exception ex）{MessageBox.Show（无法从数据库中删除组。\r\n\r\n + ex）; } 
} 
  

如果我删除联系人所属的组，则测试参照完整性，将抛出一个异常（应有的异常）：

DELETE语句与REFERENCE约束
FK_dbo.Contacts_dbo .Groups_Group_Id。冲突发生在
数据库 ContactGroups的表 dbo.Contacts的
列 Group_Id中。该语句已终止。

该语句与REFERENCE约束
FK_dbo.Contacts_dbo.Groups_Group_Id发生冲突。该冲突发生在
数据库 ContactGroups的表 dbo.Contacts的列
'Group_Id'中。被终止。

因此，很明显，当发生初始异常时，我不会清除/结束事务或其他操作。我在做什么错或遗漏？

解决方案

将WillCascadeOnDelete（true）用作WithOptional

  model_modeler.Entity< Parent>（）
 .HasMany< Child>（c => c.Children）
 .WithOptional（x => ; x.Parent）
 .WillCascadeOnDelete（true）; 
  

使用Include

  var adv = db.Adv.Include（b => b。功能）
 .Include（b => b.AdvDetails）
 .Include（b => b。 AdvGallery）
 .FirstOrDefault（b => b.Id == id）; 
 db.Adv.Remove（adv）; 
  

for .HasMany（...）。WithMany（... ）可以了

I assume this has a very simple answer. I am brand new to entity framework and I am creating a test application consisting of Contacts and Groups as objects/entities.

Here is my code to delete a group:

    private void button_DeleteGroup_Click(object sender, EventArgs e)
    {
        var _selectedGroup = dataGridView_Groups.SelectedRows[0].DataBoundItem as Group;

        try
        {
            cgContext.Groups.Remove(_selectedGroup);
            cgContext.SaveChanges();

            PopulateGroupGrid();
            MessageBox.Show("Successfully deleted group from database!");
        }
        catch(Exception ex) { MessageBox.Show("Failed to delete group from database.\r\n\r\n" + ex); }
    }

If I delete a group that a contact belongs to, to test referential integrity, an exception is thrown (as it should):

"The DELETE statement conflicted with the REFERENCE constraint "FK_dbo.Contacts_dbo.Groups_Group_Id". The conflict occurred in database "ContactGroups", table "dbo.Contacts", column 'Group_Id'. The statement has been terminated."

I then catch this exception and display a message to the user. If I then go to add a new group or contact or do anything, the transaction fails with the same exception as before:

"The DELETE statement conflicted with the REFERENCE constraint "FK_dbo.Contacts_dbo.Groups_Group_Id". The conflict occurred in database "ContactGroups", table "dbo.Contacts", column 'Group_Id'. The statement has been terminated."

So, obviously i'm not clearing / ending a transaction or something when the initial exception occurs. What am I doing wrong or missing?

解决方案

use WillCascadeOnDelete(true) for WithOptional

  modelBuilder.Entity<Parent>()
  .HasMany<Child>(c => c.Children)
  .WithOptional(x => x.Parent)
  .WillCascadeOnDelete(true);

use Include

  var adv = db.Adv.Include(b => b.Features)
                  .Include(b => b.AdvDetails)
                  .Include(b => b.AdvGallery)
                  .FirstOrDefault(b => b.Id == id);
  db.Adv.Remove(adv);

for .HasMany(...).WithMany(...) Include is ok

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