Access to database in migration

In our project we used migrations in environment with data which we don’t want to lose. Actually we are forced to use some compression directly on model. I created migration where I connect to database and, using SqlClient etc., get, transform and save data.

Connection string is saved in config.json file. We also used another config file depend on environment. Is it any possibility to access to connection string from migration or just to environment specified by -e switch in dotnet ef cli?

EF Core version: 1.0.0 Database Provider: Microsoft.EntityFrameworkCore.SqlServer

[yserious]

Actually you can access your dbContext in a migration, see: https://stackoverflow.com/questions/42644253/can-i-inject-dependency-into-migration-using-ef-core-code-first-migrations Once you have your dbContext, you can probably access the connection-string through:

        var a = _dbContext.Database.GetDbConnection().ConnectionString;

(I actually use this to add new (non-seeding) data in a separate migration. However, be very careful when changing data this way. Your _dbContext.Save is executed before any (other) migrations are run.)

[bricelam]

One alternative would be to do this while the migrations are applying in your application:

using (var db = new MyDbContext())
{
    db.Database.OpenConnection();
    try
    {
        var migrator = db.GetService<IMigrator>();
        foreach (var migration in db.Database.GetPendingMigrations())
        {
            // TODO: Do things before each migration.
            // TODO: Access database using db.Database.GetDbConnection()
            migrator.Migrate(migration);
            // TODO: Do things after each migration.
        }
    }
    finally
    {
        db.Database.CloseConnection();
    }
}