CODEWITHSUNDEEP
c#sql-serverlinq
ap.singh
ap.singh

Reputation: 1160

linq join query get single record from second table

I am using linq join to get data from two tables. But my second table has multiple records corresponding to first table. And i want only first record from second table . 

Table student
id     name 
1      a1
2      b1

Table images
id   image         studentId
1    1.jpg            1
2    2.jpg            1
3    3.jpg            2
4    4.jpg            2


Result should be 

id  name image
1   a1   1.jpg
2   b1   3.jpg

I am using the following code. and its returning four records.

 public IEnumerable<StudentBean> getStudent()
        {
             return (from p in context.student
                     join r in context.images
                      on p.id equals r.studentId


                     select new StudentBean
                    {id=p.id,
                     name =p.name,
                     image=r.image
                    }).ToList<StudentBean>();
        }

Upvotes: 6

Views: 8871

Answers (2)

Ehsan Sajjad
Ehsan Sajjad

Reputation: 62488

Your can write subquery here:

return (from p in context.student
        select new StudentBean
               {
                 id=p.id,
                 name =p.name,
                 image=(from r in context.images 
                        where r.studentId == p.id
                        select r).First().image
                }).ToList<StudentBean>();

or if there is chance that in Images table no row matches then you need to work around this way to prevent Null Reference Exeption:

return (from p in context.student
        let Image = (from r in context.images 
                        where r.studentId == p.id
                        select r).FirstOrDefault()
        select new StudentBean
               {
                 id=p.id,
                 name = p.name,
                 image = Image != null ? Image.image : null
                }).ToList<StudentBean>();

Upvotes: 5

akekir
akekir

Reputation: 523

...
join r in context.images
on p.id equals r.studentId into imgs
from r in imgs.Take(1)
...

Upvotes: 11

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