【转载】C#中传统方式进行数据库表信息查询

声明：本博客转载来源于李天平老师的《项目中的.NET》一书，推荐大家阅读，收获一定是大大的。

C#中采用传统方式进行数据库表信息查询通常有三种方式：

一、【传统的数据库查询】

// <summary>
        /// 数据库查询
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        protected void Button1_Click(object sender, EventArgs e)
        {
            string connectionString = "data source=VQJREZV7DVSK2QA;Database=codematic;user id=sa;password=admin@123456";
            using (SqlConnection myConnection = new SqlConnection(connectionString))
            {
                SqlCommand cmd = myConnection.CreateCommand();
                cmd.CommandText = "SELECT ID,Name,Descn,Price From P_Product order by ID";
                myConnection.Open();
                using (SqlDataReader dr = cmd.ExecuteReader())
                {
                    while (dr.Read())
                    {
                        Response.Write(dr.GetInt32(0).ToString() + "," + dr.GetString(1) + "<br>");
                    }
                }
            }
        }

二、【对象列表查询】

这里主要是通过泛型List<>的使用，这个类的FillAll方法接收一个委托方法来实现查询符合条件的对象。

（01）声明一个对象

    public class Man
    {
        private string name;
        private string sex;
        /// <summary>
        /// 姓名
        /// </summary>
        public string Name
        {
            set { name = value; }
            get { return name; }
        }
        /// <summary>
        /// 性别：男，女
        /// </summary>
        public string Sex
        {
            set { sex = value; }
            get { return sex; }
        }
        public Man(string Name, string Sex)
        {
            name = Name;
            sex = Sex;
        }

    }

（02）对以上对象列表进行操作：

      protected void Button2_Click(object sender, EventArgs e)
        {
            //构造对象列表
            List<Man> manlist = new List<Man>();
            manlist.Add(new Man("李天平", "男"));
            manlist.Add(new Man("李嘉诚", "男"));
            manlist.Add(new Man("徐静蕾", "女"));
            manlist.Add(new Man("随意","女"));

            //对象查询
            List<Man> mans = manlist.FindAll(
                delegate(Man man)
                {
                    return man.Sex == "男";
                }
                );

            //对象遍历输出
            foreach (Man man in mans)
            {
                Response.Write(man.Name + "," + man.Sex + "<br>");
            }
        }

三、【XML查询】

当数据存储在XML中的时候，可以从XML中查询数据。如下图所示：

  

protected void Button3_Click(object sender, EventArgs e)
        {
            XmlDocument doc = new XmlDocument();
            // 装入指定的XML文档
            string path = Server.MapPath("sampledata.xml");
            doc.Load(path);
            XmlNodeList stulist = doc.SelectNodes("//学生");//选择匹配节点
            foreach (XmlNode stu in stulist)
            {
                Response.Write(stu["姓名"].InnerText + "，" + stu["性别"].InnerText + "<br>");
            }
        }