This is a mirror of http://www.pastie.org/1977343. It appears this site is down, and I retrieved this from the Google Cache. It contains a source code sample from a Stack Overflow answer (http://stackoverflow.com/questions/12081251/mongodb-as-a-queue-capped-collection-tailable-cursor). This is the only source code example I could find online wit…

gistfile1.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;

using MongoDB.Bson;
using MongoDB.Driver;
using MongoDB.Driver.Builders;

namespace TestTailableCursor {
    public static class Program {
        public static void Main(string[] args) {
            try {
                var server = MongoServer.Create("mongodb://localhost/?safe=true");
                var database = server["test"];

                if (database.CollectionExists("capped")) {
                    database.DropCollection("capped");
                }
                var collectionOptions = CollectionOptions.SetCapped(true).SetMaxDocuments(5);
                var commandResult = database.CreateCollection("capped", collectionOptions);
                var collection = database["capped"];

                // to test the tailable cursor manually insert documents into the test.capped collection
                // while this program is running and verify that they are echoed to the console window

                // see: http://www.mongodb.org/display/DOCS/Tailable+Cursors for C++ version of this loop
                BsonValue lastId = BsonMinKey.Value;
                while (true) {
                    var query = Query.GT("_id", lastId);
                    var cursor = collection.Find(query)
                        .SetFlags(QueryFlags.TailableCursor | QueryFlags.AwaitData)
                        .SetSortOrder("$natural");
                    using (var enumerator = (MongoCursorEnumerator<BsonDocument>) cursor.GetEnumerator()) {
                        while (true) {
                            if (enumerator.MoveNext()) {
                                var document = enumerator.Current;
                                lastId = document["_id"];
                                ProcessDocument(document);
                            } else {
                                if (enumerator.IsDead) {
                                    break;
                                }
                                if (!enumerator.IsServerAwaitCapable) {
                                    Thread.Sleep(TimeSpan.FromMilliseconds(100));
                                }
                            }
                        }
                    }
                }
            } catch (Exception ex) {
                Console.WriteLine("Unhandled exception:");
                Console.WriteLine(ex);
            }

            Console.WriteLine("Press Enter to continue");
            Console.ReadLine();
        }

        private static void ProcessDocument(
            BsonDocument document
        ) {
            Console.WriteLine(document.ToJson());
        }
    }
}