protected override void Down(
MigrationBuilder migrationBuilder
)
That is, builds the operations that will take the database from the state left in by this migration so that it returns to the state that it was in before this migration was applied.
This method must be overridden in each class that inherits from Migration if both 'up' and 'down' migrations are to be supported. If it is not overridden, then calling it will throw and it will not be possible to migrate in the 'down' direction.
See Database migrations for more information and examples.