MongoDb 游标不返回集合中的所有文档

Question

I'm trying to iterate over every document in a collection and save them to an excel file. Currently there are 857 documents and I have confirmed this in Compass, but only 756 are being returned. What would stop all the documents from being returned?

At first I thought it was to do with my object mapping, but I reverted back to Bsondocuments and I get the same result. Is there something I am missing here?

                var db = client.GetDatabase("database");
                var collection = db.GetCollection<BsonDocument>("collection");
                var filter = new BsonDocument();
                using (var cursor = collection.Find(filter).ToCursor())

                    while (cursor.MoveNext())
                    {
                        int i = 1;
                        foreach (var doc in cursor.Current)

                        {
                            ;
                            sheet.Cells["A" + i.ToString()].Value = doc.ToString();
                            i++;
                            Console.WriteLine("Documents found: " + i);

Documents found: 757

Answer 1

Mongo's cursor returns documents in batches. You move from batch to batch using MoveNext and then processing the documents in Current. The code appears to this, but the counter i is reset to 1 on every batch. You will want to do something like:

            var db = client.GetDatabase("database");
            var collection = db.GetCollection<BsonDocument>("collection");
            var filter = new BsonDocument();
            using (var cursor = collection.Find(filter).ToCursor()){
                int i = 1;
                while (cursor.MoveNext())
                {                        
                    foreach (var doc in cursor.Current)

                    {
                        ;
                        sheet.Cells["A" + i.ToString()].Value = doc.ToString();
                        i++;                     
                    }
                }
                Console.WriteLine("Documents found: " + i);
             }

Alternately it may be easier to do:

    int i = 1;
    await cursor.ForEachAsync(doc => {
      sheet.Cells["A" + i.ToString()].Value = doc.ToString()
      i++;
    });
    Console.WriteLine("Documents found: " + i);

or if you aren't setup for async:

    int i = 1;
    cursor.ForEachAsync(doc => {
      sheet.Cells["A" + i.ToString()].Value = doc.ToString()
      i++;
    }).Wait();
    Console.WriteLine("Documents found: " + i);