Linq to Entities, random order

by

A simple way of doing this is to order by Guid.NewGuid() but then the ordering happens on the client side. You may be able to persuade EF to do something random on the server side, but that’s not necessarily simple – and doing it using “order by random number” is apparently broken.

To make the ordering happen on the .NET side instead of in EF, you need AsEnumerable:

IEnumerable<MyEntity> results = context.MyEntity
                                       .Where(en => en.type == myTypeVar)
                                       .AsEnumerable()
                                       .OrderBy(en => context.Random());

It would be better to get the unordered version in a list and then shuffle that though.

Random rnd = ...; // Assume a suitable Random instance
List<MyEntity> results = context.MyEntity
                                .Where(en => en.type == myTypeVar)
                                .ToList();

results.Shuffle(rnd); // Assuming an extension method on List<T>

Shuffling is more efficient than sorting, aside from anything else.
See my article on randomness for details about acquiring an appropriate Random instance though. There are lots of Fisher-Yates shuffle implementations available on Stack Overflow.

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