Castle ActiveRecord学习实践(7)级联

本章来看看Castle ActiveRecord中的级联(cascade)操作

还是以post和comment为例

post.cs 修改为

[ActiveRecord("Posts")]
public class Post : ActiveRecordBase<Post>
{
    [PrimaryKey("PostId")]
    public int Id { get; set; }

    [Property]
    public string Subject { get; set; }

    [Property]
    public string Text { get; set; }

    [Property]
    public DateTime DateAdded { get; set; }

    [BelongsTo("CategoryId")]
    public Category Category { get; set; }

    [HasMany(Lazy=true,Cascade=ManyRelationCascadeEnum.AllDeleteOrphan,Inverse = true)]
    public IList<Comment> Comments { get; set; }

    [HasAndBelongsToMany(typeof(Tag), Table = "TagPost", ColumnKey = "PostId", ColumnRef = "TagId")]
    public IList<Tag> Tag { get; set; }

}

HasMany特性添加Cascade

枚举属性

枚举	值
ManyRelationCascadeEnum	None	不做级联操作
	All	增删改都做级联操作
	AllDeleteOrphan	都做级联操作，并且删除孤儿数据。即删除没有对应Post的Comment对象
	SaveUpdate	在增加和更新的时候做级联操作
	Delete	在删除的时候做级联操作

1、级联添加

创建一个post ，并添加多个comment

//创建post
Post post = new Post();
post.DateAdded = DateTime.Now;
post.Subject = "castle active record 7";
post.Text = "content";
List<int> list = new List<int>();
list.Add(1);
list.Add(2);
post.Category = Category.Find(5);
post.Tag = Tag.FindAll();
using (TransactionScope tran=new TransactionScope ())
{
    try
    {
        post.Create();
        for (int i = 0; i < 10; i++)
        {
            //创建comment
            Comment comment = new Comment();
            comment.Author = "hzd" + i;
            comment.DateAdded = DateTime.Now;
            comment.Text = "comment" + i + " content!";
            comment.Post = post;
            comment.Save();
        }
        tran.VoteCommit();

    }
    catch
    {
        tran.VoteRollBack();
    }
}

2、级联更新

为已经存在的post 添加 comment

Post post = new Post();
post = Post.Find(8);
using (TransactionScope tran=new TransactionScope ())
{
    try
    {
        for (int i = 0; i < 5; i++)
        {
            //创建comment
            Comment comment = new Comment();
            comment.Author = "hzd-" + i;
            comment.DateAdded = DateTime.Now;
            comment.Text = "comment" + i + " content!";
            comment.Post = post;
            comment.Save();
        }
        post.Text = "castle active record  Cascade";
        post.Update();
        tran.VoteCommit();

    }
    catch
    {
        tran.VoteRollBack();
    }
}

3、级联删除

删除一个post

Post post = new Post();
post = Post.Find(1);
post.Delete();

删除一个post的一个comment

using (new SessionScope())
{
    Post post = new Post();
    post = Post.Find(8);
    int count = post.Comments.Count;
    post.Comments.RemoveAt(0);
    post.Update();
}

特别注意

[HasMany(Lazy = true, Cascade = ManyRelationCascadeEnum.AllDeleteOrphan, Inverse = true)]
public IList<Comment> Comments { get; set; }

设置One-To-Many 中 One方(本文中的post) HasManyAttribute的Inverse属性为true

Inverse属性指定了双向关联中的所有者，它的默认值为false。

Inverse 为true是，关联关系的维护者为 主表(即posts表)。

为false时，关联关系的维护者为 子表(即comments表)，如果子表设置了外键不为null，会出现

不能将值 NULL 插入列 '外键列'

的错误。