protected override void Up(MigrationBuilder migrationBuilder)
{
    migrationBuilder.CreateTable(
        name: "Countries",
        columns: table => new
        {
            Name = table.Column<string>(nullable: false),
            Population = table.Column<int>(nullable: false),
        },
        constraints: table =>
        {
            table.PrimaryKey("PK_Country", x => x.Name);
        }
    ).WithRows(new [] { // Note: we could get property names from the column names
        new { Name = "Germany", Population = 81831000 },
        new { Name = "France", Population = 65447374 },
        new { Name = "Belgium", Population = 10839905 },
    });
}

protected override void Down(MigrationBuilder migrationBuilder)
{
    migrationBuilder.DropTable(
        name: "Countries");
}