Entity Framework Include OrderBy random generates duplicate data

Question

When I retrieve a list of items from a database including some children (via .Include), and order the randomly, EF gives me an unexpected result.. I creates/clones addition

Answer 1

I also ran into this problem, and solved it by adding a Randomizer Guid property to the main class I was fetching. I then set the column's default value to NEWID() like this (using EF Core 2)

builder.Entity()
    .Property(m => m.Randomizer)
    .HasDefaultValueSql("NEWID()");

When fetching, it gets a bit more complicated. I created two random integers to function as my order-by indexes, then ran the query like this

var rand = new Random();
var randomIndex1 = rand.Next(0, 31);
var randomIndex2 = rand.Next(0, 31);
var taskSet = await DbContext.MainClasses
    .Include(m => m.SubClass1)
        .ThenInclude(s => s.SubClass2)
    .OrderBy(m => m.Randomizer.ToString().Replace("-", "")[randomIndex1])
        .ThenBy(m => m.Randomizer.ToString().Replace("-", "")[randomIndex2])
    .FirstOrDefaultAsync();

This seems to be working well enough, and should provide enough entropy for even a large dataset to be fairly randomized.