MongoDb: Optimistic Concurrency

Optimistic concurrency is one something that most of us need in our applications. What follows is a simple example on how to achieve it in MongoDB. First, a really simple document.

Note : This post uses a lot of code that I have shown in previous posts, please look at them if there is any confusion. The principles remain simple and can be used without using the code shown below.

public class Person : MongoEntity {
        public string Name { get; set; }
        public long Version { get ; set ; }
    }

Next, when you want to edit a person it becomes a simple FindAndModify.

public bool EditPerson (Person person) {
            //find the document with thr same id and version
            var query = Query.And(
                Query<Person>.EQ(_ => _.Version, person.Version), 
                Query<Person>.EQ(_ => _.Id, person.Id));

            //bump the version

            var updatedPerson = person;
            updatedPerson.Version = person.Version + 1;
            var result = PersonConnectionHandler.MongoCollection.FindAndModify(query, null, 
                Update.Replace<Person>(updatedPerson), true);

            if ( result.ModifiedDocument != null ) {
                Console.WriteLine("Document Modified successfully");
                Console.WriteLine(result.ModifiedDocument);
                return true;
            } else {
                return false;
            }
        }

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