Random Linq Query

Question

Hi guys,

how I can get a random row from a selection in my linq query?

I tried:

Bot bot = (from a in dc.Bot
           select a).OrderBy(x => Guid.NewGuid()).First();

But doesn't work, I ever get the same.

Answer 1

I would use Skip

var query = from a in dc.Bot
            select a;

int random = new Random().Next(query.Count);

Bot bot = query.Skip(random).First();

Answer 2

Something like this might work:

var random = new Random();
var allBots = (from a in dc.Bot select a);

var randomAmountToSkip = random.NextInt(allBots.Count());
var anyBot = allBots.Skip(randomAmountToSkip).First()

Answer 3

I have an extension method for that in my archive:

static class IEnumerableExtensions {

   public static T PickRandomOne<T>(this IEnumerable<T> list, Random rnd) {
      T picked = default(T);
      int cnt = 0;
      foreach (T item in list) {
         if (rnd.Next(++cnt) == 0) {
            picked = item;
         }
      }
      return picked;
   }

}

Usage:

Random rnd = new Random();
Bot bot = (from a in dc.Bot select a).PickRandomOne(rnd);

The advantage of this method is that you don't need to know how many items there are beforehand, so you don't have to run the query twice.