c# - 不使用 NHibernate 对象返回列表

Question

假设我有一个界面。

public interface IBlogRepository
{
    IList<Blog> Blogs(int pageNo, int pageSize);
    int TotalPosts();
}

现在我创建了一个类来实现它并使用 NHibernate。

using NHibernate;
using NHibernate.Criterion;
using NHibernate.Linq;
using NHibernate.Transform;
using System.Collections.Generic;
using System.Linq;

namespace JustBlog.Core
{
    public class BlogRepository: IBlogRepository
    {
        // NHibernate object
        private readonly ISession _session;

        public BlogRepository(ISession session)
        {
            _session = session;
        }

        public IList<Post> Posts(int pageNo, int pageSize)
        {
            var query = _session.Query<Post>()
                        .Where(p => p.Published)
                        .OrderByDescending(p => p.PostedOn)
                        .Skip(pageNo * pageSize)
                        .Take(pageSize)
                        .Fetch(p => p.Category);

            query.FetchMany(p => p.Tags).ToFuture();

            return query.ToFuture().ToList();
        }

        public int TotalPosts()
        {
            return _session.Query<Post>().Where(p => p.Published).Count();
        }
    }

以上代码来自网络某处for creating a blog engine .但是我根本不知道 NHibernate，我使用 Entity Framework 来完成我的工作。

如何在不使用 NHiberate 的情况下重写代码？

Answer 1

实体模型

假设我们有这样的实体模型:

public class Post
{
    public Post() { Tags = new List<Tag>(); }

    public int Id{ get; set; }
    public string Title{ get; set; }
    public string ShortDescription{ get; set; }
    public string Description{ get; set; }
    public string Meta{ get; set; }
    public string UrlSlug{ get; set; }
    public bool Published{ get; set; }
    public DateTime PostedOn{ get; set; }
    public DateTime? Modified{ get; set; }

    public int CategoryId { get; set; }
    public virtual Category Category{ get; set; }

    public virtual IList<Tag> Tags{ get; set; }
}

public class Tag
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string UrlSlug { get; set; }
    public string Description { get; set; }

    public virtual IList<Post> Posts { get; set; }
}

public class Category
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string UrlSlug { get; set; }
    public string Description { get; set; }

    public virtual IList<Post> Posts { get; set; }
}

上下文

我们的上下文类非常简单。构造函数接受 web.config 中的连接字符串的名称，我们定义了三个 DbSet:

public class BlogContext : DbContext
{
    public BlogContext() : base("BlogContextConnectionStringName") { }

    public DbSet<Category> Categories { get; set; }
    public DbSet<Post> Posts { get; set; }
    public DbSet<Tag> Tags { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);
    }
}

存储库

我们的博客存储库的界面很好，很简单，没有太大变化:

public interface IBlogRepository
{
    IEnumerable<Post> Posts(int pageNo, int pageSize);
    int TotalPosts();
}

有趣的是博客存储库本身!

public class BlogRepository : IBlogRepository
{
    // NHibernate object replace with our context
    private readonly BlogContext _blogContext;

    public BlogRepository(BlogContext blogContext)
    {
        _blogContext = blogContext;
    }

    //Function to get a list of blogs
    public IEnumerable<Post> Posts(int pageNo, int pageSize)
    {
        //We start with the blogs db set:
        var query = _blogContext.Posts
            //Filter by Published=true
            .Where(p => p.Published)
            //Order by date they were posted
            .OrderByDescending(p => p.PostedOn)
            //Jump through the list
            .Skip(pageNo * pageSize)
            //Get the required number of blogs
            .Take(pageSize)
            //Make sure the query include all the categories
            .Include(b => b.Category);

        //Just return what we have!
        return query;
    }

    //Much simpler function, should be pretty self explanatory
    public int TotalPosts()
    {
        return _blogContext.Posts.Where(p => p.Published).Count();
    }
}

后续步骤

好的，现在我们已经完成了所有设置，并且在您的 web.config 中设置了一个很好的连接字符串，我们要用它做什么？好吧，让我们写一些博客吧!

var context = new BlogContext();
var repository = new BlogRepository(context);
var posts = repository.Posts(0, 10);

然后我们可以用这些博客做一些事情:

foreach(var blog in blogs)
{
    Console.WriteLine("Blog Id {0} was posted on {1} and has {2} categories", blog.Id, blog.PostedOn, blog.Categories.Count());
}

注意事项

我没有实现 FetchMany/ToFuture 部分，因为这里不需要它们。