How to convert LINQ query result to List?

Question

I need to convert linq query result to list. I tried the following code:

var qry = from a in obj.tbCourses
                     select a;

List<course> lst = new List<course>();
lst = qry.ToList();

The following error occurred for the above code:

Cannot implicitly convert type 
System.Collections.Generic.List<Datalogiclayer.tbcourse> to
System.Collections.Generic.List<course>

how did it not help? What did you expect that didn't happen? — BrokenGlass, Apr 26 '12 at 12:42
BTW, your code could be much shorter... `var lst = obj.tbCourses.ToList();` — Thomas Levesque, Apr 26 '12 at 12:44
possible duplicate of [Syntax for linq query to List](http://stackoverflow.com/questions/7488980/syntax-for-linq-query-to-liststring) — nawfal, Sep 17 '13 at 08:59

score 31 · Accepted Answer · edited Nov 08 '12 at 12:01

31

No need to do so much works..

var query = from c in obj.tbCourses
        where ...
        select c;

Then you can use:

List<course> list_course= query.ToList<course>();

It works fine for me.

edited Nov 08 '12 at 12:01

j0k

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answered Nov 08 '12 at 11:41

dellgg

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2021 this can now be simplified to List listCourse= query.ToList(); – Loaderon Apr 19 '21 at 21:59

score 29 · Answer 2 · edited Nov 20 '13 at 22:38

29

List<course> = (from c in obj.tbCourses
                 select 
                new course(c)).toList();

You can convert the entity object to a list directly on the call. There are methods to converting it to different data struct (list, array, dictionary, lookup, or string)

edited Nov 20 '13 at 22:38

IvanH

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answered Nov 20 '13 at 22:19

goggles1200

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IMHO this is the best answer. It is not only single command, but it also illustrates that `from ... select ...` linq syntax is still keeping its meaning equivalent to standard form (`tbCourses.Select()`) – miroxlav Oct 26 '14 at 00:01

score 8 · Answer 3 · answered Apr 26 '12 at 12:48

8

You need to somehow convert each tbcourse object to an instance of course. For instance course could have a constructor that takes a tbcourse. You could then write the query like this:

var qry = from c in obj.tbCourses
          select new course(c);

List<course> lst = qry.ToList();

answered Apr 26 '12 at 12:48

Thomas Levesque

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This is creative! But, it does have one drawback that your models project would now have a dependency to your data repository. While this would be fine in a smaller project, depending on your architecture and separation of concers, this could be a problem. – msigman Apr 26 '12 at 12:50

msigman · Answer 4 · 2012-04-26T13:10:45.413

You need to use the select new LINQ keyword to explicitly convert your tbcourseentity into the custom type course. Example of select new:

var q = from o in db.Orders
        where o.Products.ProductName.StartsWith("Asset") && 
              o.PaymentApproved == true
        select new { name   = o.Contacts.FirstName + " " +
                              o.Contacts.LastName, 
                     product = o.Products.ProductName, 
                     version = o.Products.Version + 
                              (o.Products.SubVersion * 0.1)
                   };

http://www.hookedonlinq.com/LINQtoSQL5MinuteOverview.ashx

score 3 · Answer 5 · answered Jun 15 '13 at 19:20

What you can do is select everything into a new instance of Course, and afterwards convert them to a List.

var qry = from a in obj.tbCourses
                     select new Course() {
                         Course.Property = a.Property
                         ...
                     };

qry.toList<Course>();

How to convert LINQ query result to List?

5 Answers5

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