【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>");

            }

        }