Concatenate many rows into a single text string in Entity framework

Question

Consider a database table holding names, with three rows:

SubjectID      StudentName
---------      -------------
 1             Peter
 2             Paul
 2             Mary

Is there an easy way to turn this into a single string in entity framework? something like this:

SubjectID       StudentName
----------      -------------
1               Peter
2               Paul, Mary

Check this link to more information.

1) what have you tried? 2) the inputs/outputs don't match! 3) your output example is arbitrary. what's the logic? — Grant Thomas
– Grant Thomas, Commented May 28, 2013 at 12:33
please check stackoverflow.com/questions/194852/… for more info — Hossein Moradinia
– Hossein Moradinia, Commented May 28, 2013 at 12:35
Your example output still defies your request. What do you want, and where are you stuck with it? — Grant Thomas
– Grant Thomas, Commented May 28, 2013 at 12:41

Dave New · Accepted Answer · 2013-05-28 13:21:21Z

7

You can use GroupBy to group your students by subject:

var result = StudentSubjects
                .GroupBy(x => x.SubjectID)
                .Select(x => new 
                    { 
                        Subject = x.Key, 
                        Names = String.Join(", ", x.Select(n => n.Name)) 
                    });

I have used String.Join to concatenate the list of names.

edited May 28, 2013 at 13:21

answered May 28, 2013 at 12:45

Dave New

40.3k62 gold badges235 silver badges412 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Moayad Myro Over a year ago

I got error LINQ to Entities does not recognize the method 'System.String Join

Arsen Khachaturyan Over a year ago

This code wouldn't work unless you call ToList() or ToListAsync(cancelationToken) before .Select(). But doing so will also harm the performance of the query.

Collectives™ on Stack Overflow

Concatenate many rows into a single text string in Entity framework

1 Answer 1

2 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related