不使用NHibernate对象返回列表

时间:2014-05-20 15:04:11

标签: c# entity-framework nhibernate ef-code-first

假设我有一个界面。

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

现在我创建了一个实现它的类并使用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for creating a blog engine上的某个地方。但是我根本不了解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?

2 个答案:

答案 0 :(得分:3)

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; }
}

<强>上下文

我们的上下文类非常简单。构造函数接受web.config中连接字符串的名称,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);
    }
}

<强>存储库

我们博客存储库的界面非常简单且不会发生太大变化:

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

它是博客存储库本身,事情变得有趣!

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web.config中设置了一个很好的连接字符串,我们该如何处理呢?好吧,让我们来一些博客!

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

然后我们可以对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());
}

备注

我没有实施FetchMany/ToFuture部分,因为这里不需要它们。

答案 1 :(得分:0)

一种简单的方法是使用Linq to Entities从数据库映射模型。

首先,在数据库中创建与您链接的帖子中定义的对象完全相同的表格,记住添加关系。

然后添加一个ADO实体数据模型并从数据库中选择这些表填充它,您将以XXXEntities结束,这是一个ObjectContext,其中已经创建了所有类。

最后,执行查询将是这样的(将您的实体命名为BlogEntities):

public IEnumerable<Blog> Posts(int pageNo, int pageSize)
{

    using(BlogEntities con = new BlogEntities())
    {

        var query = con.Post.Include("Category") //<-- If you set "Pluralize fields and properties" when creating your model, it will be "Posts" and "Categories"
                    .Where(p => p.Published)
                    .OrderByDescending(p => p.PostedOn)
                    .Skip(pageNo * pageSize)
                    .Take(pageSize)
                    .ToList();

        return query;

    }

}

public int TotalPosts()
{
    using(BlogEntities con = new BlogEntities())
    {

          return con.Post.Where(p => p.Published).Count();

    }

}