public static async Task mainAsync() { var db = new MongoClient().GetDatabase("school"); var collection = db.GetCollection<BsonDocument>("students"); var list = await collection.Find(new BsonDocument()).ToListAsync(); var newList = new List<BsonDocument>(); list.ForEach(data => newList.Add(dropScore(data))); await db.DropCollectionAsync("students"); await db.CreateCollectionAsync("students"); await collection.InsertManyAsync(newList); }