Недопустимое имя столбца "Age2".

  migrationBuilder.AddColumn<int>(
                name: "Age2",
                table: "Users9",
                nullable: false,
                defaultValue: 0);

            ApplicationContext db = new ApplicationContext();

            var command = db.Database.GetDbConnection().CreateCommand();

            command.CommandText = string.Format("update users9 set Age2 = {0}", 199);
            db.Database.OpenConnection();

            command.ExecuteNonQuery();

command.CommandText = string.Format("update users9 set \"Age2\" = {0}", 199);

   protected override void Up(MigrationBuilder migrationBuilder)
        {
            BeforeDelTables();

            migrationBuilder.DropTable(
                name: "Users8");

            migrationBuilder.CreateTable(
                name: "Users9",
                columns: table => new
                {
                    Id = table.Column<int>(nullable: false)
                        .Annotation("SqlServer:ValueGenerationStrategy", SqlServerValueGenerationStrategy.IdentityColumn),
                    Name = table.Column<string>(nullable: true),
                    Age = table.Column<int>(nullable: false)
                },
                constraints: table =>
                {
                    table.PrimaryKey("PK_Users9", x => x.Id);
                });

            AfterAddTables(migrationBuilder);
        }

 void BeforeDelTables()
        {
            ApplicationContext db = new ApplicationContext();

            var command = db.Database.GetDbConnection().CreateCommand();

            command.CommandText = "SELECT * From users8";
            db.Database.OpenConnection();

            using (var reader = command.ExecuteReader())
            {
                while (reader.Read())
                {
                    us9 u9 = new us9();

                    u9.Name = reader["Name"].ToString();
                    u9.Age = (int)reader["Age"];

                    _users9.Add(u9);
                }
            }

        }

        void AfterAddTables(MigrationBuilder migrationBuilder)
        {
            foreach (var u9 in _users9)
                migrationBuilder.Sql(string.Format(@"insert into dbo.users9 (Name, Age) values ('{0}', {1})", u9.Name, u9.Age));
            
        }