Which LINQ statement is better and why?

Question

In both of the statements I am trying to fetch the ID of Category which has the name as specified in the variable;

Both work fine. What is the difference and which one is better?

string name = "Progreammers";

var categoryID = from c in DataContext.Categories
                             where c.Name == name
                             select c.CategoryID;

var categoryID  = 
  DataContext.Categories.Single(c => c.Name == name).CategoryID;

EDIT: There is only one Name(field) for every CategoryID(field) in the table.

the type of categoryID will be different in your sample code — Fredou, Jan 26 '10 at 19:03
sure it is, In DB it is Bigint, in code it is long. but I can't get what do you mean ? — Asad, Jan 26 '10 at 19:11
what I mean is the first one will be, I think, an IEnumerable while the second will be a long — Fredou, Jan 26 '10 at 19:14

score 12 · Accepted Answer · edited Nov 26 '10 at 23:37

12

The two statements perform different functions.

The first could return multiple records.

The second will only return a single CategoryID. It will also throw an exception if at least one record is not found.

The following query would be the equivalent to your first statement:

var categoryID = DataContext.Categories.Where(c => c.Name == name).CategoryID;

And the following is the query syntax equivalent to the second statement:

var categoryID = (from c in DataContext.Categories
                 where c.Name == name
                 select c.CategoryID).Single();

Either way, consistency is probably the most important (performance should be on par with each other since they're both executed the same way). If you use query syntax, stick with it. If you start using lambda expressions, use them as much as you can.

edited Nov 26 '10 at 23:37

Peter Mortensen

30,738
21
105
131

answered Jan 26 '10 at 18:58

Justin Niessner

242,243
40
408
536

Also, if there is no record with the given ID, the second will throw. – Marcel Gosselin Jan 26 '10 at 19:00
Thanks for the equivalent for the first one.What is equivalent for the first statement without => expression ? Thanks – Asad Jan 26 '10 at 19:05
@asdi - Added the query syntax for the second statement. – Justin Niessner Jan 26 '10 at 19:14

score 3 · Answer 2 · edited Nov 26 '10 at 23:38

3

They are not the same.

The first one will return a list if there are many matches.

The second one will only return one.

edited Nov 26 '10 at 23:38

Peter Mortensen

30,738
21
105
131

answered Jan 26 '10 at 18:59

Fredou

19,848
10
58
113

score 0 · Answer 3 · edited May 23 '17 at 12:19

0

As already noted the two are different but I think the purpose of your question is asking if there is a difference between "SQL" style and "Lambda" style LINQ expressions.

If so, there is a similar question here:

LINQ: Dot Notation vs Query Expression

edited May 23 '17 at 12:19

Community

1
1

answered Jan 26 '10 at 19:08

HitLikeAHammer

2,679
3
37
53

Query syntax is really just converted into the lambda syntax by the compiler, so as long as both statements are truly written to do the same thing they are equivalent. – Chris Pitman Jan 26 '10 at 22:09

Which LINQ statement is better and why?

3 Answers3