麻烦会的大神帮忙注释一下，新手不懂！！！！！

Question

 SqlConnection conn = new SqlConnection();//实例化对象
                    string conStr = @"Data Source=WHIZENDT016\SQLEXPRESS;Initial Catalog=Users;Integrated Security=True";
                    conn.ConnectionString = conStr;
                    conn.Open();
                    SqlCommand cmd = new SqlCommand("select * from Users_id where Id='" + textBox1.Text + "'and Password ='" + textBox2.Text + "'", conn);
                    SqlDataReader str = cmd.ExecuteReader();
                    str.Read();

Answer 1

           SqlConnection conn = new SqlConnection();//实例化对象
            //數據庫連接字符串
            string conStr = @"Data Source=WHIZENDT016\SQLEXPRESS;Initial Catalog=Users;Integrated Security=True";
            conn.ConnectionString = conStr;
            //打開連接
            conn.Open();
            //執行sql 命令
            SqlCommand cmd = new SqlCommand("select * from Users_id where Id='" + textBox1.Text + "'and Password ='" + textBox2.Text + "'", conn);
            //按READER方式執行查詢
            SqlDataReader str = cmd.ExecuteReader();
            //此次可循環READ，逐條取得結果
            str.Read();