Linq-to-Entities Left JOIN

Question

This is my query:

from forum in Forums
    join post in Posts on forum equals post.Forum into postGroup    

    from p in postGroup     
    where p.ParentP         


        

Answer 1

 public class ForumPosts 
    {
        public Forum Forum { get; set; }
        public IQueryable Posts { get; set; }
    }

    public class DisplaySet 
    {
        public string Name { get; set; }
        public string PostTile { get; set; }
    } 



          //left outer join
            using (ClassLibrary1.Entities context = new Entities())
            {
                var allForums = from f in context.Fora
                                select new ForumPosts
                                {
                                    Forum = f,
                                    Posts = context.Posts.Where(x=> x.ForumId == f.ForumId)

                                };
                List ds = new List();

                foreach (var forum in allForums)
                {
                    if (forum.Posts.AsEnumerable().Count() != 0)
                    {
                        foreach (var post in forum.Posts)
                        {
                           ds.Add(new DisplaySet(){ Name = forum.Forum.Name, PostTile = post.PostValue});
                        }
                    }
                    else
                        ds.Add(new DisplaySet(){ Name = forum.Forum.Name, PostTile = string.Empty});
                }

                foreach (var item in ds)
                {
                    Console.WriteLine(string.Format("{0} || {1}",item.Name,item.PostTile));
                }


            }



//This produces the following LINQ query which is right
SELECT 
[Project1].[ForumId] AS [ForumId], 
[Project1].[Name] AS [Name], 
[Project1].[C1] AS [C1], 
[Project1].[PostId] AS [PostId], 
[Project1].[PostValue] AS [PostValue], 
[Project1].[ForumId1] AS [ForumId1]
FROM ( SELECT 
    [Extent1].[ForumId] AS [ForumId], 
    [Extent1].[Name] AS [Name], 
    [Extent2].[PostId] AS [PostId], 
    [Extent2].[PostValue] AS [PostValue], 
    [Extent2].[ForumId] AS [ForumId1], 
    CASE WHEN ([Extent2].[PostId] IS NULL) THEN CAST(NULL AS int) ELSE 1 END AS [C1]
    FROM  [dbo].[Forum] AS [Extent1]
    LEFT OUTER JOIN [dbo].[Post] AS [Extent2] ON [Extent2].[ForumId] = [Extent1].[ForumId]
)  AS [Project1]
ORDER BY [Project1].[ForumId] ASC, [Project1].[C1] ASC