Randomly Select Records Using Linq to SQL

Question

i want to retrieve 15 records from a table of around 50 records. but i want all records to be generated randomly. if i take a random number and write something like:

var result = (from r in sc.Subjects
              where (r.SubName == sub && r.Level == lev)
              select r).skip(randomnumber).take(10),

the starting record will be random but the next 9 will be in sequence. so any idea on how i can have all 10 records random using linq to sql?

You can use the first approach in this [answer](http://stackoverflow.com/a/648247/181108). — Stefan, Jan 06 '12 at 15:31
Also check this out: http://msdn.microsoft.com/en-us/library/cc441928.aspx — Ray, Jan 06 '12 at 15:33

score 8 · Answer 1 · answered Jan 06 '12 at 15:34

8

I use this in one of my sites, to show random ads from a table. Its EF4.0, but the Linq2SQL is probably the same or similar:

myAds = (from q in db.Ads select q).OrderBy(x => Guid.NewGuid()).Take(10).ToList();

answered Jan 06 '12 at 15:34

E.J. Brennan

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msarchet · Accepted Answer · 2012-01-07T22:59:27.087

0

It would probably be better to do this with a for loop to get the item then using LINQ

var result = new List<subject>();
for(i = 0; i < 10; i++) 
{
   randomnumber = GenerateNewRandomNumber();
   result.Add(sc.Subjects.Where(r => r.SubName == sub && r.Level == lev).Skip(randomnumber).take(1).First;

}

edited Jan 07 '12 at 22:59

answered Jan 06 '12 at 15:29

msarchet

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How do you know the maximum value that you can skip? – Rich O'Kelly Jan 06 '12 at 16:01
hey, your method seems to be pretty good but im getting the following error: The best overloaded method match for 'System.Collections.Generic.List.Add(Genre)' has some invalid arguments – Yash Upadhyay Jan 06 '12 at 17:15
After the Take(1) add a `First`, right now it is Returning an IEnumberable instead of a Genre – msarchet Jan 06 '12 at 19:07
i am still getting the same error! searched many forums and read all about list but can't get rid of this error! – Yash Upadhyay Jan 07 '12 at 11:16

Rich O'Kelly · Answer 3 · 2012-01-06T16:00:32.497

0

Try the following:

private static Random Generator = new Random();
...
var result = sc.Subjects.Where(s => s.SubName == sub && s.Level == lev).OrderBy(s => Generator.Next()).Take(10);

edited Jan 06 '12 at 16:00

answered Jan 06 '12 at 15:30

Rich O'Kelly

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Randomly Select Records Using Linq to SQL

3 Answers3