CSharpMongoMigrations

What is it?

CSharpMongoMigrations is an alternative .NET library for MongoDB migrations. Unlike the official package, it supports both Up and Down migrations, which can be a significant advantage for large-scale MongoDB projects. In addition, it has no dependencies on outdated MongoDB drivers, so there's no need to manage multiple driver versions anymore.

Documentation API

Generally, there are four main types of migrations:

1. Common migration

   [Migration(0, "Add John Doe")]
    public class AddPersonMigration : Migration
    {
        public override void Up()
        {
            var collection = GetCollection("Persons");
            var document = new BsonDocument();

            document.AddUniqueIdentifier(new Guid("06BFFCF5-DAE9-422A-85AB-F58DE41E86DA"));
            document.AddProperty("Name", "John Doe");
            
            collection.InsertOne(document);
        }

        public override void Down()
        {
            var collection = GetCollection("Persons");
            var idFilter = Builders<BsonDocument>.Filter.Eq("_id", new Guid("06BFFCF5-DAE9-422A-85AB-F58DE41E86DA"));
            collection.DeleteOne(idFilter);
        }
    }

In this example, we define the Up migration to add John Doe to the Person collection. The Down method rolls back the migration, restoring the database to its original state. Take note of the Migration attribute — it's required for the migration to be executed by the launcher. You must specify a unique migration number (e.g., '0') and provide a descriptive label (e.g., 'Add John Doe').

2. Document migration

These migrations allow to apply changes to each document in the specified collection.

   [Migration(1, "Change persons")]
    public class AddPropertyPersonMigration : DocumentMigration
    {
        protected override string CollectionName { get { return "Persons"; } }
               
        protected override void UpgradeDocument(BsonDocument document)
        {
            document.AddProperty("IsActive", true);            
        }

        protected override void DowngradeDocument(BsonDocument document)
        {
            document.RemoveProperty("IsActive");
        }
    }

3. Collection migration

These migrations allow to apply changes to each collection separately from another ones.

   [Migration("Animals", 0)]
    public sealed class AddAnimalMigration : Migration
    {
        public override void Up()
        {
            var collection = GetCollection("Animals");
            var document = new BsonDocument();

            document.AddUniqueIdentifier(new Guid("2A7B73A8-3C4A-422D-90B4-C73BCF48EBD4"));
            document.AddProperty("Kind", "Cat");

            collection.InsertOne(document);
        }

        public override void Down()
        {
            var collection = GetCollection("Animals");
            var idFilter = Builders<BsonDocument>.Filter.Eq("_id", new Guid("2A7B73A8-3C4A-422D-90B4-C73BCF48EBD4"));
            collection.DeleteOne(idFilter);
        }
    }

Here, the Migration attribute specifies the target collection name and the migration version for a predefined collection. This enables migrations to be applied to a specific schema.

4. Conditional migration

These migrations can be conditionally skipped based on predefined criteria.

    [Migration(4, "Add Migration when condition meets")]
    public sealed class ConditionalMigrations : Migration
    {
        public override void Up()
        {
            var collection = GetCollection("Persons");
            var document = new BsonDocument();

            document.AddUniqueIdentifier(new Guid("20C2CAC4-C55D-4C5C-8937-33698A3EC6C7"));
            document.AddProperty("Name", "John Doe - Conditional");

            collection.InsertOne(document);
        }

        public override void Down()
        {
            var collection = GetCollection("Persons");
            var idFilter = Builders<BsonDocument>.Filter.Eq("_id", new Guid("20C2CAC4-C55D-4C5C-8937-33698A3EC6C7"));
            collection.DeleteOne(idFilter);
        }

        // Up condition
        public override bool ShouldUp()
        {
            return true;
        }

        // Down condition
        public override bool ShouldDown()
        {
            return false;
        }
    }

For more in-depth examples, check out the CSharpMongoMigrations.Demo project.

How to launch migrations?

It’s actually quite simple: just create an instance of the MigrationRunner class.

   var runner = new MigrationRunner("<mongoDb_connection_string>", "<database_name>", "<full_name_of_assembly_with_migrations>");

You can then call the Up or Down method to apply or revert migrations.

   // Apply all migrations before specified version.
   // Use -1 as a version parameter to apply all existing migrations. ('-1' is a default parameter value)
   runner.Up("<version>"); 
   
   // Roll back all migrations after specified version.
   // Use -1 as a version parameter to downgrade all existing migrations. ('-1' is a default parameter value)
   runner.Down("<version>"); 

By default, these methods execute all defined migration types. To run migrations for a specific collection, use one of the available polymorphic overloads.

   // Apply all migrations before specified version.
   // Use -1 as a version parameter to apply all existing migrations for the target collection. ('-1' is a default parameter value)
   runner.Up("<Collection_name>", "<version>"); 
   
   // Roll back all migrations after specified version.
   // Use -1 as a version parameter to downgrade all existing migrations for the target collection. ('-1' is a default parameter value)
   runner.Down("<Collection_name>", "<version>");