using MongoDB.Bson;
using MongoDB.Driver;

var client = new MongoClient("mongodb://localhost:27017");
var database = client.GetDatabase("foo");
var collection = database.GetCollection<BsonDocument>("bar");
await collection.InsertOneAsync(new BsonDocument("Name", "Jack"));
var list = await collection.Find(new BsonDocument("Name", "Jack"))
    .ToListAsync();
foreach(var document in list)
{
    Console.WriteLine(document["Name"]);
}

using MongoDB.Bson;
using MongoDB.Driver;

public class Person
{
    public ObjectId Id { get; set; }
    public string Name { get; set; }
}

var client = new MongoClient("mongodb://localhost:27017");
var database = client.GetDatabase("foo");
var collection = database.GetCollection<Person>("bar");
await collection.InsertOneAsync(new Person { Name = "Jack" });
var list = await collection.Find(x => x.Name == "Jack")
    .ToListAsync();
foreach(var person in list)
{
    Console.WriteLine(person.Name);
}