Hi,
   UpdateOneAsync() and UpdateManyAsync() are the two functions used to update the data in the mongodb using C# we can replace the one value with other or else we can increment the value by certain number.

            In the below example for UpdateOneAsync() I am updating single document in a MongoDB collection. I am updating MasterID as 11 for the record which contains MasterID as 10.

            In the below example for UpdateManyAsync() I am updating multiple document in a MongoDB collection. Incrementing value to 10 for the values of MasterID contains greater than 100

C#: .Net 4.5 and MongoDB 2.0

using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using MongoDB.Bson;
using MongoDB.Driver;
using MongoDB.Driver.Core;

namespace UpdColl
{
    class Program
    {
        static void Main(string[] args)
        {
            callMain(args).Wait();
            Console.ReadLine();
        }
        static async Task callMain(string[] args)
        {
            var conString = "mongodb://localhost:27017";
            var Client = new MongoClient(conString);
            var DB = Client.GetDatabase("test");
            var collection = DB.GetCollection<BsonDocument>("MasterIds");
           
            //below code will update one record of the data
            var updoneresult = await collection.UpdateOneAsync(
                                Builders<BsonDocument>.Filter.Eq("MasterID", 10),
                                Builders<BsonDocument>.Update.Set("MasterID", 11));

            //below code will update multiple records of the data
            var updmanyresult = await collection.UpdateManyAsync(
                                Builders<BsonDocument>.Filter.Gt("MasterID", 100),
                                Builders<BsonDocument>.Update.Inc("MasterID", 10));
           
            //below code retrieves the updated records
            await collection.Find(new BsonDocument())
                .ForEachAsync(x => Console.WriteLine(x));
        }
    }
}