Why is C# and MongoDB Driver code connecting, but failing to Write?

Question

Here is the information about my development environment:

• Microsoft Visual Studio Community 2015
• .NET Framework 4.6
• ASP.NET MVC assembly System.Web.Mvc Version=5.2.3.0
• MongoDB.Driver 2.0.1.27
• Mongodb 3.0.6

Within my C# application, I have the following code that retrieves a MongoDB database reference:

public class MongoDBConnectionManager {
    public IMongoDatabase getMongoDB() {
        var client = new MongoClient("mongodb://localhost:27017");
        MongoClient(System.Configuration.ConfigurationManager.ConnectionStrings["MongoDB"].ConnectionString);

        MongoServer.Create("Server=localhost:27017");
        IMongoCollection <BsonDocument> UserDetails = iMgDb.GetCollection<BsonDocument>("Users");

        return iMgDb;
    }
}

Here is the POCO class that represent a User Business Entity:

using MongoDB.Bson.Serialization.Attributes;

public class UserModel {
    [BsonId]
    public int ID { get; set; }

    [Required]
    [BsonElement]
    public string UserName { get; set; }

    [Required]
    [BsonElement]
    public string Password { get; set; }

    [Required]
    [BsonElement]
    public string Email { get; set; }

    [BsonElement]
    public string PhoneNo { get; set; }

    [BsonElement]
    public string Address { get; set; }
}

Here is the DAO C# class that uses the Mongo DB Connection Manager Class:

public class DAO {
    public async Task<int> insertNewUser(UserModel um) {
        MongoDBConnectionManager mgoDBCntMng = new MongoDBConnectionManager();

        IMongoDatabase database = mgoDBCntMng.getMongoDB();

        IMongoCollection <UserModel> UserDetails = database.GetCollection<UserModel>("Users");

        try {
            Task getTask = UserDetails.InsertOneAsync(um);
            await getTask;
        } catch(Exception) {
        }
        return 0;
    }
}

When I run the application, I can see the following information logged in the DOS Command Prompt window where I started the mongoDB. If you look towards the end of the Dos Command Prompt, you will notice 2 connections being made:

C:\Program Files\MongoDB\Server\3.0\bin>mongod --dbpath ./data/db

2015-09-23T12:23:07.896+0530 I JOURNAL  [initandlisten] journal 
dir=./data/db\jo

urnal

2015-09-23T12:23:07.900+0530 I JOURNAL  [initandlisten] recover : no 
journal fil

es present, no recovery needed

2015-09-23T12:23:08.060+0530 I JOURNAL  [durability] Durability thread started

2015-09-23T12:23:08.062+0530 I JOURNAL  [journal writer] Journal writer thread s

tarted

2015-09-23T12:23:08.283+0530 I CONTROL  [initandlisten] MongoDB starting 
: pid=1

2936 port=27017 dbpath=./data/db 64-bit host=My-PC

2015-09-23T12:23:08.283+0530 I CONTROL  [initandlisten] targetMinOS: 
Windows 7/W

indows Server 2008 R2

2015-09-23T12:23:08.284+0530 I CONTROL  [initandlisten] db version v3.0.6

2015-09-23T12:23:08.284+0530 I CONTROL  [initandlisten] git version: 
1ef45a23a4c

5e3480ac919b28afcba3c615488f2

2015-09-23T12:23:08.284+0530 I CONTROL  [initandlisten] build info: 
windows sys.

getwindowsversion(major=6, minor=1, build=7601, platform=2, 
service_pack='Servic

e Pack 1') BOOST_LIB_VERSION=1_49

2015-09-23T12:23:08.285+0530 I CONTROL  [initandlisten] allocator: 
tcmalloc

2015-09-23T12:23:08.285+0530 I CONTROL  [initandlisten] options: { 
storage: { db

Path: "./data/db" } }

2015-09-23T12:23:08.321+0530 I NETWORK  [initandlisten] waiting for 
connections

on port 27017

2015-09-23T12:24:20.326+0530 I NETWORK  [initandlisten] connection 
accepted from

 127.0.0.1:65065 #1 (1 connection now open)

2015-09-23T12:24:22.332+0530 I NETWORK  [initandlisten] connection 
accepted from

 127.0.0.1:65066 #2 (2 connections now open)

I'm really stumped as to how to resolve the problem. I tried to search the MongoDB error log using DOS command prompt, but it shows NO errors. From MongoDB client using DOS command prompt, I got the following:

C:\Program Files\MongoDB\Server\3.0\bin>mongo
MongoDB shell version: 3.0.6
connecting to: test
> use foo
switched to db foo
> db.runCommand( { getLastError: 1, w: 1, wtimeout:5000 } )
{
        "connectionId" : 6,
        "n" : 0,
        "syncMillis" : 0,
        "writtenTo" : null,
        "err" : null,
        "ok" : 1
}

The problem that I am facing is that the point of execution runs smoothly, but fails to write to the database.
What is wrong with the way I use async and wait in the said code?

Could someone please tell me how to correct the problem?

Answer 1

It took a while, but the problem was caused by the fact that I mistakenly used the int basic data type for the ID in the UserModel as opposed to ObjectId.

Here is the corrected code for the UserModel:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Web;
using System.ComponentModel.DataAnnotations;
using System.Web.Mvc;
using MongoDB.Bson;
using MongoDB.Driver;
using MongoDB.Driver.Linq;
using WebApplication1.Models;
using MongoDB.Bson.Serialization.Attributes;

namespace WebApplication1.Models
{
    public class UserModel
    {

        [BsonId]
        public ObjectId ID { get; set; }

        [Required]
        [BsonElement]
        public string UserName { get; set; }

        [Required]
        [BsonElement]
        public string Password { get; set; }

        [Required]
        [BsonElement]
        public string Email { get; set; }

        [BsonElement]
        public string PhoneNo { get; set; }

        [BsonElement]
        public string Address { get; set; }
    }
}