Example C# code showing MongoDB Transactions using the MongoDB .NET Driver (2.7+)

CSharpTransactions.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using MongoDB.Bson;
using MongoDB.Driver;
using MongoDB.Bson.Serialization.Attributes;

namespace MongoDBTransaction
{
    class Program
    {
        public class Product
        {
            [BsonId]
            public ObjectId Id { get; set; }
            [BsonElement("SKU")]
            public int SKU { get; set; }
            [BsonElement("Description")]
            public string Description { get; set; }
            [BsonElement("Price")]
            public Double Price { get; set; }
        }
       
        const string MongoDBConnectionString = "mongodb+srv://<<MONGODB CONNECTION STRING>>";
 
        static async Task Main(string[] args)
        {
           if (!await UpdateProducts()) { Environment.Exit(0); }
            Console.WriteLine("Finished updating the product collection");
            Console.ReadKey();
        }
        static async Task<bool> UpdateProducts()
        {
            //Create client connection to our MongoDB database
            var client = new MongoClient(MongoDBConnectionString);

            //Create a session object that is used when leveraging transactions
            var session = client.StartSession();

            //Create the collection object that represents the "products" collection
            var products = session.Client.GetDatabase("MongoDBStore").GetCollection<Product>("products");
           
            //Clean up the collection if there is data in there
            products.Database.DropCollection("products");

            //Create some sample data
            var TV = new Product { Description = "Television", SKU = 4001, Price = 2000 };
            var Book = new Product { Description = "A funny book", SKU = 43221, Price = 19.99 };
            var DogBowl = new Product { Description = "Bowl for Fido", SKU = 123, Price = 40.00 };

            //Begin transaction
            session.StartTransaction();

            try
            {
                //Insert the sample data 
                await products.InsertOneAsync(TV);
                await products.InsertOneAsync(Book);
                await products.InsertOneAsync(DogBowl);

                var filter = new FilterDefinitionBuilder<Product>().Empty;
                var results = await products.Find<Product>(filter).ToListAsync();
                Console.WriteLine("Original Prices:\n");
                foreach (Product d in results)
                {
                    Console.WriteLine(String.Format("Product Name: {0}\tPrice: {1:0.00}", d.Description, d.Price));
                }

                //Increase all the prices by 10% for all products
                var update = new UpdateDefinitionBuilder<Product>().Mul<Double>(r=>r.Price,1.1);
                await products.UpdateManyAsync(filter, update); //,options);

                //Made it here without error? Let's commit the transaction
                session.CommitTransaction();

                //Let's print the new results to the console
                Console.WriteLine("Original Prices:\n");
                results = await products.Find<Product>(filter).ToListAsync();
                foreach (Product d in results)
                {
                    Console.WriteLine(String.Format("Product Name: {0}\tPrice: {1:0.00}", d.Description, d.Price));
                }
            }
            catch (Exception e)
            {
                Console.WriteLine("Error writing to MongoDB: " + e.Message);
                session.AbortTransaction();
            }
            return true;
        }
      }
}

Thanks for this piece of code but... your gist might be obsolete?
You should call InsertOneAsync with session as 1st parameter, otherwise the operations are run outside the transaction. To observe this behavior: replace CommitTransaction by AbortTransaction... all written data is still persisted.
Documentation says:

When a transaction aborts, all data changes made by the writes in the transaction are discarded without ever becoming visible and the transaction ends.

https://docs.mongodb.com/manual/reference/command/abortTransaction/

Thanks for this piece of code but... your gist might be obsolete?
You should call InsertOneAsync with session as 1st parameter, otherwise the operations are run outside the transaction. To observe this behavior: replace CommitTransaction by AbortTransaction... all written data is still persisted.
Documentation says:

When a transaction aborts, all data changes made by the writes in the transaction are discarded without ever becoming visible and the transaction ends.

https://docs.mongodb.com/manual/reference/command/abortTransaction/

Man, thanks for the help!
I also forgot to put current client session in to CRUD operation then my problem has been solved as well

Thanks for sharing mate

Thank you for this code.
Didn't you forget to dispose of the session?

Thank you for this code. Didn't you forget to dispose of the session?

Yeah, it should be disposed.