Linq Orderby random ThreadSafe for use in ASP.NET
asp.net, asp.net-mvc, linq, s#arp-architecture
Solution
One way to achieve efficiently is to add a column to your data `Shuffle` that is populated with a random int (as each record is created).
The query to access the table then becomes ...
Random random = new Random();
int seed = random.Next();
result = result.OrderBy(s => (~(s.Shuffle & seed)) & (s.Shuffle | seed)); // ^ seed);
This does an XOR operation in the database and orders by the results of that XOR.
Advantages:-
- Efficient: SQL handles the ordering, no need to fetch the whole table
- Repeatable: (good for testing) - can use the same random seed to generate the same random order
- Works on most (all?) Entity Framework supported databases
This is the approach used by my home automation system to randomize playlists. It picks a new seed each day giving a consistent order during the day (allowing easy pause / resume capabilities) but a fresh look at each playlist each new day.
Problem
i'm using Asp.net MVC with Sharp Architecture. I have this code: ``` return _repositoryKeyWord.FindAll(x => x.Category.Id == idCAtegory) .Take(50).ToList(); ``` How can i order by random? Note: i don't want to order the 50 extracted items, i want order before and then extract 50 items. thks