using var context = new SomeDbContext();
context.Database.EnsureDeleted();
context.Database.EnsureCreated();

context.AddRange(
    new Order { Id = 1, Foo = 1 },
    new Order { Id = 2, Foo = 1 },
    new Order { Id = 3, Foo = 1 },
    new Order { Id = 4, Foo = 3 },
    new Order { Id = 5, Foo = 3 },
    new Order { Id = 6, Foo = 3 });

context.SaveChanges();

var results = context.Set<Order>().OrderBy(o => o.Foo).ThenByDescending(o => o.Foo).ToList();
foreach (var result in results)
{
    Console.WriteLine($"{result.Id} {result.Foo}");
}

public class SomeDbContext : DbContext
{
    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder) 
        => optionsBuilder
            //.UseSqlite("DataSource = db.dat")
            .UseMongoDB("mongodb://localhost:27017", "SomeDb3")
            .LogTo(Console.WriteLine, LogLevel.Information);

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Order>();
    }
}

public class Order
{
    public int Id { get; set; }
    public int Foo { get; set; }
}

Unhandled exception. System.InvalidOperationException: Duplicate element name 'Foo'.
   at MongoDB.Bson.BsonDocument.Add(BsonElement element)
   at MongoDB.Bson.BsonDocument.AddRange(IEnumerable`1 elements)
   at MongoDB.Bson.BsonDocument..ctor(IEnumerable`1 elements)
   at MongoDB.Driver.Linq.Linq3Implementation.Ast.AstSortFields.Render()
   at MongoDB.Driver.Linq.Linq3Implementation.Ast.Stages.AstSortStage.Render()
   at MongoDB.Driver.Linq.Linq3Implementation.Ast.AstPipeline.<>c.<Render>b__10_0(AstStage s)
   at System.Linq.Enumerable.IListSelectIterator`2.MoveNext()
   at MongoDB.Bson.BsonArray.AddRange(IEnumerable`1 values)
   at MongoDB.Bson.BsonArray..ctor(IEnumerable`1 values)
   at MongoDB.Driver.Linq.Linq3Implementation.Ast.AstPipeline.Render()
   at MongoDB.Driver.Linq.Linq3Implementation.Translators.ExpressionToExecutableQueryTranslators.ExecutableQuery`3.RenderPipeline()
   at MongoDB.Driver.Linq.Linq3Implementation.Translators.ExpressionToExecutableQueryTranslators.ExecutableQuery`3.Execute(IClientSessionHandle session, CancellationToken cancellationToken)
   at MongoDB.Driver.Linq.Linq3Implementation.MongoQueryProvider`1.Execute[TResult](ExecutableQuery`2 executableQuery, CancellationToken cancellationToken)
   at MongoDB.Driver.Linq.Linq3Implementation.MongoQuery`2.Execute()
   at MongoDB.Driver.Linq.Linq3Implementation.MongoQuery`2.GetEnumerator()
   at MongoDB.EntityFrameworkCore.Query.QueryingEnumerable`2.Enumerator.MoveNextHelper()
   at MongoDB.EntityFrameworkCore.Query.QueryingEnumerable`2.Enumerator.MoveNext()
   at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
   at Program.<Main>$(String[] args) in /Users/arthur.vickers/code/OnYourOwnNow/OnYourOwnNow/Program.cs:line 20