如何將左外連接 sql 查詢轉換為實體框架 5.0？

Question

   using (database db = new database())
           { 
             var query = (
                          from c in db.tblBlogs

                         join a in db.tblBlogMedias on c.id equals  a.BlogId 


                         select new
                        {

                            c.id,
                            c.CreatedDate,
                            c.Author,
                            c.BlogTitle,
                            c.BlogDescription,
                            a.BlogId,
                            a.BlogPicturePath


                        }).OrderByDescending(d => d.id).ToList();


            System.Text.StringBuilder sb = new System.Text.StringBuilder();
           query.ToList().ForEach(x =>
                    {          


                            sb.Append(string.Format("<div  class='col-sm-4 
wow fadeInUp animated' data-wow-duration='1000ms' data-wow-delay='400ms' 
style='visibility: visible; animation-duration: 1000ms; animation-delay: 
400ms; animation-name: fadeInUp;'><div class='post-thumb'><div class='post-
meta'>"+
                                                     "</div>"+
                                                    "</div>"+
                                                    "<div class='entry-
header'><h3><a href='#'>{0}</a></h3><span class='date'>{1}</span></div>
</div>",x.BlogTitle,x.CreatedDate));

                    });
                 }

如何在 var query = 中編寫此 sql 查詢：

select tblBlog.*,tblBlogMedia.BlogPicturePath from tblBlog left outer join 
tblBlogMedia on tblBlog.id = tblBlogMedia.BlogId
where tblBlogMedia.id=(select max(id) from tblBlogMedia where BlogId='2')

Answer 1

使用正確命名的實體和導航屬性，它看起來像這樣：

using System;
using System.Collections.Generic;
using System.Data.Entity;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace EfDbFirstTest
{
    public class Blog
    {
        public int Id { get; set; }
        public DateTime CreatedDate { get; set; }
        public string Author { get; set; }
        public string BlogTitle { get; set; }
        public string BlogDescription { get; set; }
        public ICollection<BlogMedia> BlogMedia { get; set; }
    }

    public class BlogMedia
    {
        public int Id { get; set; }
        public int BlogId { get; set; }
        public Blog Blog { get; set; }
        public string BlogPicturePath { get; set; }
    }

    public class Db : DbContext
    {
        public DbSet<Blog> Blogs { get; set; }
        public DbSet<BlogMedia> BlogMedia { get; set; }
    }
    class Program
    {
        static void Main(string[] args)
        {


            using (var db = new Db())
            {
                db.Database.Log = m => Console.WriteLine(m);

                var q = from b in db.Blogs
                        select new
                        {

                            b.Id,
                            b.CreatedDate,
                            b.Author,
                            b.BlogTitle,
                            b.BlogDescription,
                            BlogPicturePath = b.BlogMedia.Any() ? b.BlogMedia.OrderByDescending(m => m.Id).FirstOrDefault().BlogPicturePath : null
                        };

                var results = q.ToList();



                Console.ReadKey();
            }
        }
    }
}

Answer 2

這就是我想要的完美工作方式，我在 ForEach 循環體中編寫此代碼，然后在 sb.append 中傳遞 q 的值：

                  var q = (from d in db.tblBlogMedias
                         join c in db.tblBlogs on d.BlogId equals x.id
                         select new
                         {
                             d.Id,
                             d.BlogPicturePath
                         }).OrderByDescending(d=>d.Id).Max(d => d.BlogPicturePath);