Readme_old.md

LiteDB.Migration

LiteDB.Migration is a lightweight, easy-to-use library designed to facilitate schema migrations for LiteDB databases in .NET applications. It provides a structured way to evolve your database schema over time, ensuring that your application can safely and efficiently migrate data as your models change.

Features

• Flexible Migration Paths: Migrate data across multiple versions with ease.
• Simple API: Define your migrations using a simple API.
• Implicit and Explicit Migrations: Migrate all at once or in a Lazy way.

Getting Started

Installation

LiteDB.Migration is available as a NuGet package. You can install it via the NuGet Package Manager or the CLI:

dotnet add package LiteDB.Migration

Basic Usage

Get started by following the steps below. For a full example, see the Tests

1. Define Your Models: Start by defining your document models. For each version change that requires a migration, prepare a new version of the model.

// Original model
public class ModelV1
{
    public int Id { get; set; }
    public string OldProperty { get; set; }
}

// Updated model
public class ModelV2
{
    public int Id { get; set; }
    public string NewProperty { get; set; }
}

2. Implement Migrations: Create a migration class for each model transformation. Inherit from MigrationBase<TFrom, TTo> and implement the migration logic.

public class ModelV1_to_ModelV2_Mapper : MigrationBase<ModelV1, ModelV2>
{
    public override int? From => 1; // Original version
    public override int To => 2;   // New version

    public override ModelV2 Migrate(ModelV1 model)
    {
        return new ModelV2
        {
            Id = model.Id,
            NewProperty = $"New-{model.OldProperty}"
        };
    }
}

3. Create a Migration Set: Create a migration set to group your migrations together. Implement the IMigrationSet interface and return a list of your migrations.

public class MigrationSet_1_to_2 : IMigrationSet
{
    public MigrationSetItem[] Items => new[]
    {
        // ModelV2 is the marker class, The Mapper will be used to migrate Model to ModelV2
        new MigrationSetItem(nameof(ModelV2), new ModelX_to_ModelY_Mapper())
    };
}

4. Configure and Apply Migrations: Use the MigrationContainer to configure and apply your migrations.

using (var db = new LiteDatabase("YourDatabase.db"))
{
    var container = new MigrationContainer(config =>
    {
        config.WithSet<YourMigrationSet>();
        
        // The generic type is the type of the marker class
        config.Collection<ModelV2>("YourCollectionName");
    });

    container.Apply(db);
}

Contributing

Contributions are welcome! Feel free to submit pull requests, report issues, or suggest new features.

License

LiteDB.Migration is released under the MIT License. See the LICENSE file for more details.