反射入门-浅谈反射用途_根据Ado游标对象创建list集合

本人大二菜鸟一只,今天在上课期间有个同学看着C#反射的内容说反射没什么用,一时之间也想不到什么更好的例子,就写了个根据泛型类型和游标反射创建List集合的Demo.

首先创建一个用于封装对应数据的entity,代码如下.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Test
{
    public class EUserInfo
    {
        public int UserId { get; set; }
        public string UserCode { get; set; }
        public string UserName { get; set; }
        public string UserPwd { get; set; }
        public string Gender { get; set; }

        public override string ToString()
        {
            return "UserId:"+UserId+"|UserCode:"+UserCode+"|UserName:"+UserName+"|UserPwd:"+UserPwd+"|Gender:"+Gender;
        }
    }
}

这里我重写了ToString方法,以便待会儿更直观的看到效果.

接下来创建EUserInfo实体类对应的table,sql如下:

use master
go
if exists (select * from sys.databases where name='reflectDemoDB')
drop database reflectDemoDB
create database reflectDemoDB
go
use reflectDemoDB
go
create table UserInfo(
    UserId int primary key identity,
    UserCode ) not null,
    UserName ) not null,
    UserPwd  ) not null,
    Gender   ) check(Gender in ('男','女'))
)
go
','男')
','男')
','男')

　　为了可以方便操作ado对象我这里写了一个工具类DBHelper,代码如下:

　　

using System;
using System.Collections.Generic;
using System.Web;
using System.Data.SqlClient;
using System.Data;
using System.Configuration;

namespace Test
{
    /// <summary>
    ///DBHelper：数据库访问操作类
    /// </summary>
    public class DBHelper
    {
        /// <summary>
        /// 更新操作：增，删，改 共用
        /// </summary>
        /// <param name="sql"></param>
        /// <returns>bool</returns>
        public static bool UpdateOpera(string sql,params SqlParameter[] sps)
        {
            SqlCommand cmd = new SqlCommand(sql, Connection);
            //////////////////将配置参数加入到Command中
            cmd.Parameters.AddRange(sps);
            /////////////////
            ;
        }

        /// <summary>
        /// 单个查询操作：返回首行首列数据
        /// </summary>
        /// <param name="sql">查询SQL语句</param>
        /// <returns>object</returns>
        public static object GetScalar(string sql, params SqlParameter[] sps)
        {
            SqlCommand cmd = new SqlCommand(sql, Connection);
            //////////////////将配置参数加入到Command中
            cmd.Parameters.AddRange(sps);
            /////////////////
            return cmd.ExecuteScalar();
        }

        /// <summary>
        /// 多行查询操作：返回SqlDataReader
        /// </summary>
        /// <param name="sql">查询SQL语句</param>
        /// <returns>SqlDataReader</returns>
        public static SqlDataReader GetReader(string sql, params SqlParameter[] sps)
        {
            SqlCommand cmd = new SqlCommand(sql, Connection);
            //////////////////将配置参数加入到Command中
            cmd.Parameters.AddRange(sps);
            /////////////////
            return cmd.ExecuteReader();
        }

        /// <summary>
        /// 多行查询操作：返回DataTable
        /// </summary>
        /// <param name="sql">查询SQL语句</param>
        /// <returns>DataTable</returns>
        public static DataTable GetDataTable(string sql, params SqlParameter[] sps)
        {
            DataTable dt = new DataTable();
            SqlDataAdapter dad = new SqlDataAdapter(sql, Connection);
            //////////////////将配置参数加入到Command中
            dad.SelectCommand.Parameters.AddRange(sps);
            /////////////////
            dad.Fill(dt);
            return dt;
        }

        public static List<string> GetColumnsByTableName(string tableName)
        {
            List<string> columnList = new List<string>();
            string sql = "select name from syscolumns where id=object_id(@tableName)";
            SqlDataReader sdr = GetReader(sql, new SqlParameter("@tableName", tableName));
            while (sdr.Read())
            {
                columnList.Add(sdr["name"].ToString());
            }
            sdr.Close();
            return columnList;
        }

        private static SqlConnection _connection;
        /// <summary>
        /// Connection对象
        /// </summary>
        public static SqlConnection Connection
        {
            get
            {
                string connectionString = "Data Source=.;Initial Catalog=reflectDemoDB;Integrated Security=True";
                if (_connection == null)
                {
                    _connection = new SqlConnection(connectionString);
                    _connection.Open();
                }
                else if (_connection.State == ConnectionState.Closed)
                {
                    _connection.Open();
                }
                else if (_connection.State == ConnectionState.Broken || _connection.State == ConnectionState.Open)
                {
                    _connection.Close();
                    _connection.Open();
                }
                return _connection;
            }
        }
    }
}

　　接下来就可以进入主题了,我这里是用一个BaseDao做例子,代码如下:

using System;
using System.Collections.Generic;
using System.Data.SqlClient;
using System.Linq;
using System.Reflection;
using System.Text;
using System.Threading.Tasks;

namespace Test
{
    public class BaseDao<T>
    {
        /// <summary>
        /// 获取泛型对应的实体类类名当做表名
        /// </summary>
        private static string TableName
        {
            get
            {
                return typeof(T).Name.Replace("E","");
            }
        }
        /// <summary>
        /// 获取泛型对应实体类所有属性
        /// </summary>
        private static PropertyInfo[] Properties { get { return typeof(T).GetProperties(); } }
        /// <summary>
        /// 通用查询所有方法
        /// </summary>
        /// <returns></returns>
        public List<T> GetAll()
        {
            //根据获取的表名拼装出sql语句
            string sql = "select * from " + TableName;
            SqlDataReader sdr = DBHelper.GetReader(sql);
            return CreateInstanceListOfSqlDataReader<T>(sdr);
        }
        private static T CreateInstance<T>(SqlDataReader sdr)
        {
            //或许泛型类所有属性

            //根据泛型T创建它的实例
            T t = (T)Activator.CreateInstance(typeof(T));
            //遍历该类所有属性
            foreach (PropertyInfo pro in Properties)
            {
                //判断属性类型 如果是对应类型就强转进行赋值
                if (pro.PropertyType.Equals(typeof(DateTime)))
                    try
                    {
                        pro.SetValue(t, Convert.ToDateTime(sdr[pro.Name]));//利用游标根据属性名获取对应列值给属性赋值
                    }
                    catch (Exception)
                    {
                        throw new Exception("转换DateTime类型失败,[" + pro.Name + "]字段[value=" + sdr[pro.Name].ToString() + "]格式不正确");
                    }
                else if (pro.PropertyType.Equals(typeof(int)))
                    try
                    {
                        pro.SetValue(t, Convert.ToInt32(sdr[pro.Name]));
                    }
                    catch (Exception)
                    {
                        throw new Exception("转换int类型失败,[" + pro.Name + "]字段[value=" + sdr[pro.Name].ToString() + "]格式不正确");
                    }
                else if (pro.PropertyType.Equals(typeof(double)))
                    try
                    {
                        pro.SetValue(t, Convert.ToDouble(sdr[pro.Name]));
                    }
                    catch (Exception)
                    {
                        throw new Exception("转换Double类型失败,[" + pro.Name + "]字段[value=" + sdr[pro.Name].ToString() + "]格式不正确");
                    }
                else
                    pro.SetValue(t, sdr[pro.Name]);
            }
            return t;
        }
        /// <summary>
        /// 根据游标sdr创建一个所传类型对象集合并返回
        /// </summary>
        /// <typeparam name="T">泛型类型</typeparam>
        /// <param name="sdr">游标</param>
        /// <returns></returns>
        private List<T> CreateInstanceListOfSqlDataReader<T>(SqlDataReader sdr)
        {
            List<T> tList = new List<T>();
            while (sdr.Read())
            {
                T t = CreateInstance<T>(sdr);
                tList.Add(t);
            }
            return tList;
        }
    }
}

　　BaseDao写好以后我们就可以看看效果了,接下来我们创建一个UserInfoDao,来继承BaseDao,代码如下:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Test
{
    public class UserInfoDao:BaseDao<EUserInfo>{}
}

　　然后我们就可以开始测试了,下面是测试代码:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Test
{
    class Program
    {
        static void Main(string[] args)
        {
            UserInfoDao userInfoDao = new UserInfoDao();
            List<EUserInfo> userInfoList = userInfoDao.GetAll();
            foreach (EUserInfo userInfo in userInfoList)
            {
                Console.WriteLine(userInfo);
            }
            Console.ReadKey();
        }
    }
}

　　这里我们可以直接调用BaseDao的GetAll方法,sql会自动在BaseDao中帮我们拼装好,得到的结果如下:

　　

　　这里我们可以看见的效果是BaseDao帮我们把数据库中表的数据封装到了对象中.不需要我们手动的来进行实例化赋值,希望这个Demo能对初学反射的有点启发,有什么不足之处大家多多指教.