Castle ActiveRecord学习实践(6)延迟加载

前言

前面的几章介绍了Castle ActiveRecord如何处理关系映射，以及面向对象中的继承。在ActiveRecord中把数据库表之间的关联关系采用对象间的聚合关系来表现，这会带来一个问题，查询post的时候会连带着查询comment。本章的内容就是处理这个问题

启用延迟加载

HasMany特性Lazy设置为true

[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)]
    public IList<Comment> Comments { get; set; }

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

}

调用延迟加载

前面的代码代表已经启用延迟加载，调用的时候做下修改

using (new SessionScope())
{
    Post post = new Post();
    post = Post.Find(1);
    int count = post.Comments.Count;
    foreach (var c in post.Comments)
    {
        Response.Write(c.Text);
    }
}

需要注意 SessionScope