MongoDB Realm – Simple example

Here is a simple example on how to use MongoDB Realm with C#.

What is MongoDB Realm?

MongoDB Realm will combine Realm, the popular mobile database and data synchronization technology, and MongoDB Stitch, the serverless platform for MongoDB, into a unified solution that makes it easy for you to build powerful and engaging experiences on more devices. See realm.io

So basically, it’s a offline first database framework that helps you to manage the two ways synchronization issue. Really useful for mobile apps.

How to use MongoDB Realm?

1. Download the Realm NuGet Package
2. Configure your Realm DB with RealmConfiguration
3. Get an instance of Realm with Realm.GetInstance()
4. Insert your objects into the DB with realm.Add() and realm.Write()
5. Retreive your object with realm.All() or realm.Find()

How to use MongoDB Realm with C#?

Follow this simple tutorial to understand the basics of Realm with C#:

using Realms;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;

namespace Realm_Demo
{
    class Program
    {
        static async Task Main(string[] args)
        {
            Realm realm = null;
            RealmConfiguration config = null;

            try
            {
                //If you don't want to store in a file
                //config = new InMemoryConfiguration("some-identifier");

                //Set the path of your db file
                var dbName = "MyRealmDb.realm";
                config = new RealmConfiguration(dbName);

                //Get the Realm instance
                realm = await Realm.GetInstanceAsync(config);
                //Get the db path
                string dbFullPath = realm.Config.DatabasePath;

                //Create a new Employee and link it to a new Company
                var employee1Name = "Elon Musk";
                var employee1 = new Employee { Name = employee1Name, Salary = 5000 };
                var company1 = new Company { Name = "SpaceX" };
                company1.Employees.Add(employee1); //There is no setter in the IList!

                //Let's create an other employee containing a mistake that we will fix later on
                var employee2 = new Employee { Name = "Jeff Beeezo", Salary = 7000 };
                var company2 = new Company { Name = "Blue Origin" };
                company2.Employees.Add(employee2);

                //THIS IS HOW TO WRITE IN REALM DB IN 3 DIFFERENT WAYS:

                // 1) Update and persist objects with a thread-safe transaction
                await realm.WriteAsync((tmpRealm) =>
                {
                    tmpRealm.RemoveAll(); //Clean the db
                    tmpRealm.Add(company1);
                    tmpRealm.Add(company2);
                });

                // 2) Using Realm commit in a transaction that can rollback the changes
                using (Transaction transaction = realm.BeginWrite())
                {
                    employee2.Name = "Jeff Bezo"; //update the name of our employee
                    transaction.Commit();
                }

                // 3) Query and update from any thread
                var myTask = new Thread(() =>
                {
                    var realm2 = Realm.GetInstance(config);
                    var theBoss = realm2.All<Employee>().Where(x => x.Name == employee1Name).First();
                    realm2.Write(() => theBoss.Salary = 10000);
                });

                myTask.Start();
                myTask.Join();

                //Refresh the Realm instance
                realm.Refresh();

                //Display what we have in the DB now:
                foreach (var company in realm.All<Company>())
                {
                    Console.WriteLine($"Company Name: {company.Name}");

                    foreach (var employee in company.Employees)
                        Console.WriteLine($"\tEmployee Name: {employee.Name}\r\n\tSalary: {employee.Salary}");
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine($"An error occurred: {ex.Message}");
            }
            finally
            {
                //Cleaning
                realm.Dispose();
                //Realm.DeleteRealm(config); //Delete the db
            }

            Console.WriteLine("\r\nPress any key...");
            Console.ReadKey();
        }
    }

    public class Employee : RealmObject
    {
        public string Name { get; set; }
        public int Salary { get; set; }
    }

    public class Company : RealmObject
    {
        public string Name { get; set; }
        public IList<Employee> Employees { get; }
    }
}
Code language: C# (cs)

Happy coding! 🙂

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