Test.cs

using LoremNET;
using MongoDB.Bson;
using MongoDB.Driver;
using System;
using System.Diagnostics;
using System.Linq;

namespace ConsoleApp6
{
    class Program
    {
        class TestDocument
        {
            public string Id { get; set; }

            public string Text { get; set; }

            public int Number { get; set; }
        }

        static void Main(string[] args)
        {
            var mongoClient = new MongoClient("mongodb://localhost");
            var mongoDatabase = mongoClient.GetDatabase("Test");
            var mongoCollection = mongoDatabase.GetCollection<TestDocument>("test");

            var generate = false;

            if (generate)
            {
                var random = new Random();

                var pos = Console.CursorTop;

                for (var i = 0; i < 100000; i++)
                {
                    var document = new TestDocument
                    {
                        Id = Guid.NewGuid().ToString(),
                        Number = random.Next(int.MaxValue),
                        Text = Lorem.Paragraph(200, 20)
                    };

                    mongoCollection.InsertOne(document);

                    Console.SetCursorPosition(0, pos);
                    Console.WriteLine("Documents: {0}", i);
                }
            }

            for (var i = 0; i < 10; i++)
            {
                var w = Stopwatch.StartNew();

                var test1 = mongoCollection
                    .Aggregate()
                    .Project<TestDocument>(Builders<TestDocument>.Projection.Include(x => x.Id).Include(x => x.Number))
                    .SortBy(x => x.Number)
                    .Skip(5).Limit(200).ToList();

                var ids = test1.Select(x => x.Id).ToList();

                var all = mongoCollection.Find(Builders<TestDocument>.Filter.In("_id", ids)).ToList();

                w.Stop();

                Console.WriteLine("Elapsed {0}", w.Elapsed);
            }

            for (var i = 0; i < 10; i++)
            {
                var w = Stopwatch.StartNew();

                var test2 = mongoCollection.Find(new BsonDocument()).Project(Builders<TestDocument>.Projection.Exclude(x => x.Text)).Skip(1).SortBy(x => x.Number).Limit(200).ToList();

                w.Stop();

                Console.WriteLine("Elapsed {0}", w.Elapsed);
            }

            var test3 = mongoCollection.Find(new BsonDocument()).Project(Builders<TestDocument>.Projection.Exclude(x => x.Text)).Skip(1000).SortBy(x => x.Number).Limit(200).ToList();
            var test4 = mongoCollection.Find(new BsonDocument()).Skip(1000).SortBy(x => x.Number).Limit(200).ToList();
        }
    }
}