Query data using LINQ to SQL and Entity Framework with foreign key?

Question

There is a problem I need help with your query on the data using LINQ to SQL and Entity Framework (I'm using Visual Studio 2010).

I have three tables:

tblNewsDetails
tblNewsCategories
tblNewsInCategories

(See photo 1 in the picture below.)

Now, I want to retrieve records in the tblNewsDetails table, with condition CategoryId=1, as shown in photo 2 in the picture below.

But NewsID and CategoryId in tblNewsInCategories table are two foreign keys. I do not see them and I do not know how to use them in my code.

Also, my code has errors, shown in photo 3 in the picture below.

http://img.tamtay.vn/files/photo2/2010/5/28/10/962/4bff3a3b_1093f58f_untitled-1.gif

I really doubt you're using LINQ to SQL and Entity Framework at the same time... You're probably using Linq to Entities, not Linq to SQL — Thomas Levesque
– Thomas Levesque, Commented May 28, 2010 at 8:18

Dynami Le Savard · Accepted Answer · 2010-05-28 04:18:21Z

There's a couple approaches possible, here's one of em

from n in tblNewsInCategories.Include("NewsCategory").Include("NewsDetail") where n.NewsCategory.CategoryID == 1 select n.NewsDetail

remember that n (and b, in your exemple) are TblNewsInCategories entities, which probably have the following properties :

{ public int NewsInCategories { get; set; } // your middle table primary key public TblNewsCategory NewsCategory { get; set; } // a navigation property public TblNewsDetails NewsDetail { get; set; } // a navigation property }

so in order to access NewsId and CategoryId, you have to go through the navigation properties.

Thank you very much Dynami Le-Savard. I have solved this problem. (I've lost three days to try to solve). You're a good person, and have good knowledge. I want to make friends with you on facebook :-)

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