Add Migration

The common solution is using C# itself as the language of migration script. So we'll need

• A package that provides the migration features
• A cli tool to auto generate source files represents the migration.

Add dependency

dotnet add package Microsoft.EntityFrameworkCore.Tools

dotnet tool install -g dotnet-ef

Add a migration

How migration organized

The following will generate a class with two parts inside your project as Migrations/<timestamp>_<class_name>.cs and Migration/<timestamp>_<class_name>.Designer.cs.

dotnet-ef migrations add <class_name>

• Migration.Up will be invoked when upgrading to this version of migration.
• Migration.Down will be invoked when reverting to previous migration.

using Microsoft.EntityFrameworkCore.Migrations;

/// <inheritdoc />
public partial class <class_name> : Migration
{
    /// <inheritdoc />
    protected override void Up(MigrationBuilder migrationBuilder) { /* ... */ }

    /// <inheritdoc />
    protected override void Down(MigrationBuilder migrationBuilder) { /* ... */ }
}

Another part of your migration takes the job of modeling, it stores the status of the schema when generating this migration.

[DbContext(typeof(MoviesContext))]
[Migration("<timestamp>_<class_name>")]
partial class <class_name>
{
    /// <inheritdoc />
    protected override void BuildTargetModel(ModelBuilder modelBuilder) { /* ... */ }
}

How snapshot organized

Adding migration also generates or updates snapshot of the current schema, it represents the current status so that migrations can have it as a reference to do reversion or upgrade

INFO

• A migration was only generated once.
• Snapshot updates on every migration.

WARNING

You should never manually edit snapshot or migrations except altering columns