MongoDB geospatial index in C#

Question

I have been trying to get started but run into the same rock time after time trying to create and query MongoDB with C# official driver. The problem is how to create data with geo information. I am just not finding the answer.

Code:

MongoUrl url = new MongoUrl("mongodb://xxx.xx.x.xx/mydb");
MongoServer server = MongoServer.Create(url);
MongoDatabase database = server.GetDatabase("mydb");

<-- this works fine

BsonDocument[] batch = {
                         new BsonDocument {
                                             { "name", "Bran" },
                                             { "loc", "10, 10" }
                                         },
                                        new BsonDocument {
                                            { "name", "Ayla" },
                                            { "loc", "0, 0" }
                                        }
            };

places.InsertBatch(batch);

<-- that part is wrong somehow

places.EnsureIndex(IndexKeys.GeoSpatial("loca"));
var queryplaces = Query.WithinCircle("loca", 0, 0, 11);
var cursor = places.Find(queryplaces);
foreach (var hit in cursor)
{
    foreach (var VARIABLE in hit)
    {
        Console.WriteLine(VARIABLE.Value);
    }
}

<-- I think that part should show both documents, now showing none. A simple find shows them both. Would be happy for some help.

Answer 1

example below is in C# (it's important to note order in the array which is longitude, latitude- follows the more logical order of x,y as opposed to the more commonly used form where latitude precedes longitude) :

1.) first your class needs to have this:

public double[] Location { get; set; }

public double Latitude
{
    get { return _latitude; }
    set
    {
        Location[1] = value;
        _latitude = value;
    }
}

public double Longitude
{
    get { return _longitude; }
    set
    {
        Location[0] = value;
        _longitude = value;
    }
}

public MyClass()
{
    Location = new double[2];
}

2.) then here is some code to get you started with the official C# driver and doing an insert w/ use of geo indexing:

    /// <summary>
    /// Inserts object and creates GeoIndex on collection (assumes TDocument is a class
    /// containing an array double[] Location where [0] is the x value (as longitude)
    /// and [1] is the y value (as latitude) - this order is important for spherical queries.
    /// 
    /// Collection name is assigned as typeof(TDocument).ToString()
    /// </summary>
    /// <param name="dbName">Your target database</param>
    /// <param name="data">The object you're storing</param>
    /// <param name="geoIndexName">The name of the location based array on which to create the geoIndex</param>
    /// <param name="indexNames">optional: a dictionary containing any additional fields on which you would like to create an index
    /// where the key is the name of the field on which you would like to create your index and the value should be either SortDirection.Ascending
    /// or SortDirection.Descending. NOTE: this should not include geo indexes! </param>
    /// <returns>void</returns>
    public static void MongoGeoInsert<TDocument>(string dbName, TDocument data, string geoIndexName, Dictionary<string, SortDirection> indexNames = null)
    {
        Connection connection = new Connection(dbName);
        MongoCollection collection = connection.GetMongoCollection<TDocument>(typeof(TDocument).Name, connection.Db);
        collection.Insert<TDocument>(data);
        /* NOTE: Latitude and Longitude MUST be wrapped in separate class or array */
        IndexKeysBuilder keys = IndexKeys.GeoSpatial(geoIndexName);
        IndexOptionsBuilder options = new IndexOptionsBuilder();
        options.SetName("idx_" + typeof(TDocument).Name);
        // since the default GeoSpatial range is -180 to 180, we don't need to set anything here, but if
        // we wanted to use something other than latitude/longitude, we could do so like this:
        // options.SetGeoSpatialRange(-180.0, 180.0);

        if (indexNames != null)
        {
            foreach (var indexName in indexNames)
            {
                if (indexName.Value == SortDirection.Decending)
                {
                    keys = keys.Descending(indexName.Key);
                }
                else if (indexName.Value == SortDirection.Ascending)
                {
                    keys = keys.Ascending(indexName.Key);
                }
            }
        }

        collection.EnsureIndex(keys, options);

        connection.Db.Server.Disconnect();
    }


using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using MongoDB.Bson;
using MongoDB.Driver;

namespace MyMongo.Helpers
{
    public class Connection
    {
        private const string DbName = "";
        private const string Prefix = "mongodb://";
        //private const string Server = "(...):27017/";
        private const string Server = "localhost:27017/";
        private const string PassWord = "";
        private const string UserName = "";
        private const string Delimeter = "";
        //if using MongoHQ
        //private const string Delimeter = ":";
        //private const string Prefix = "mongodb://";
        //private const string DbName = "(...)";
        //private const string UserName = "(...)";
        //private const string Server = "@flame.mongohq.com:(<port #>)/";
        //private const string PassWord = "(...)";
        private readonly string _connectionString = string.Empty;

        public MongoDatabase Db { get; private set; }
        public MongoCollection Collection { get; private set; }

        public Connection()
        {
            _connectionString = Prefix + UserName + Delimeter + PassWord + Server + DbName;
        }

        public Connection(string dbName)
        {
            _connectionString = Prefix + UserName + Delimeter + PassWord + Server + DbName;
            Db = GetDatabase(dbName);
        }

        //mongodb://[username:password@]hostname[:port][/[database][?options]]
        public MongoDatabase GetDatabase(string dbName)
        {
            MongoServer server = MongoServer.Create(_connectionString);
            MongoDatabase database = server.GetDatabase(dbName);
            return database;
        }

        public MongoCollection<TDocument> GetMongoCollection<TDocument>(string collectionName, MongoDatabase db, SafeMode safeMode = null)
        {
            if (safeMode == null) { safeMode = new SafeMode(true); }
            MongoCollection<TDocument> result = db.GetCollection<TDocument>(collectionName, safeMode);
            return result;
        }
    }
}

Answer 2

After looking and searching I found the answer here: https://github.com/karlseguin/pots-importer/blob/master/PotsImporter/NodeImporter.cs

This to be read with my first piece of code as this fixes it.

  MongoCollection<BsonDocument> places =
               database.GetCollection<BsonDocument>("places");

            BsonDocument[] batch = {
                                       new BsonDocument { { "name", "Bran" }, { "loc", new BsonArray(new[] { 10, 10 }) } },
                                       new BsonDocument { { "name", "Ayla" }, { "loc", new BsonArray(new[] { 0, 0 }) } }
            };

            places.InsertBatch(batch);

            places.EnsureIndex(IndexKeys.GeoSpatial("loc"));

            var queryplaces = Query.WithinCircle("loc", 5, 5, 10);
            var cursor = places.Find(queryplaces);
            foreach (var hit in cursor)
            {
                Console.WriteLine("in circle");
                foreach (var VARIABLE in hit)
                {
                    Console.WriteLine(VARIABLE.Value);

                }
            }

As a point of clarification: The problem with the code in the question is that location information should not be stored as a string, but rather as an array of 2 elements (x, y).