[转]C#反射，根据反射将数据库查询数据和实体类绑定，并未实体类赋值

Posted 2020-08-26 Danny Chen

本文来自：http://www.cnblogs.com/mrchenzh/archive/2010/05/31/1747937.html

/*****************************************
* 说明：利用反射将数据库查询的内容自动绑定
*       到实体类
*
* 时间：1:49 2009-9-19
*
* 程序员：王文壮
* ***************************************/
/****************数据库脚本***************
* create database MySchool
* go
* use MySchool
* go
* create table Student
* (
* ID int identity primary key,
* Name varchar(10)
* )
* ****************************************/
using System;
using System.Reflection;
using System.Data.SqlClient;
using System.Data;
using System.Collections.Generic;

namespace ReflectionDemo
{
    #region Main
    class Program
    {
        static void Main(string[] args)
        {
            DataSet ds = new DataSet();

            #region 连接数据库构建DataSet

            //SqlConnection con = new SqlConnection("Data Source=.;Initial Catalog=MySchool;Integrated Security=True");
            //SqlDataAdapter objAdapter = new SqlDataAdapter("Select * from student", con);
            //objAdapter.Fill(ds);

            #endregion

            #region 手动构建DataSet

            DataTable dt = new DataTable();
            dt.Columns.Add("ID");
            dt.Columns.Add("Name");
            DataRow row = dt.NewRow();
            row["ID"] = 1;
            row["Name"] = "灰太狼";
            dt.Rows.Add(row);
            ds.Tables.Add(dt);
            #endregion

            List<Student> students = new List<Student>();
            foreach (DataRow dataRow in ds.Tables[0].Rows)
            {
                Student stu = new Student();
                Utility.ConvertToEntity(stu, row);
                students.Add(stu);
            }
            foreach (Student student in students)
            {
                Console.WriteLine(student.Name);
            }
        }
    }
    #endregion

    #region 实体类

    /// <summary>
    /// 实体类，需要在属性
    /// 上添加自定义特性
    /// 每个实体类对应数据表里
    /// 的一个字段，注意，自定义特性里的参数
    /// 一定要和数据表里的字段一一对应，
    /// 否则就反射不到了！
    /// </summary>
    public class Student
    {
        [DataContextAttribute("ID")]
        public int ID { get; set; }
        [DataContext("Name")]
        public string Name { get; set; }
    }

    #endregion

    #region 自定义特性

    /// <summary>
    /// 自定义特性
    /// </summary>
    [AttributeUsage(AttributeTargets.Property)]
    public class DataContextAttribute : Attribute
    {
        /// <summary>
        /// 自定义特性
        /// </summary>
        /// <param name="fieldName">数据表字段名称</param>
        public DataContextAttribute(string property) { this.Property = property; }
        /// <summary>
        /// 数据表字段属性(实体属性)
        /// </summary>
        public string Property { get; set; }
    }

    #endregion

    #region 反射

    public class Utility
    {
        /// <summary>
        /// 将DataRow转换成实体
        /// </summary>
        /// <param name="obj">实体</param>
        /// <param name="row">数据表一行数据</param>
        public static void ConvertToEntity(object obj, DataRow row)
        {
            ///得到obj的类型
            Type type = obj.GetType();
            ///返回这个类型的所有公共属性
            PropertyInfo[] infos = type.GetProperties();
            ///循环公共属性数组
            foreach (PropertyInfo info in infos)
            {
                ///返回自定义属性数组
                object[] attributes = info.GetCustomAttributes(typeof(DataContextAttribute), false);
                ///将自定义属性数组循环
                foreach (DataContextAttribute attribute in attributes)
                {
                    ///如果DataRow里也包括此列
                    if (row.Table.Columns.Contains(attribute.Property))
                    {
                        ///将DataRow指定列的值赋给value
                        object value = row[attribute.Property];
                        ///如果value为null则返回
                        if (value == DBNull.Value) continue;
                        ///将值做转换
                        if (info.PropertyType.Equals(typeof(string)))
                        {
                            value = row[attribute.Property].ToString();
                        }
                        else if (info.PropertyType.Equals(typeof(int)))
                        {
                            value = Convert.ToInt32(row[attribute.Property]);
                        }
                        else if (info.PropertyType.Equals(typeof(decimal)))
                        {
                            value = Convert.ToDecimal(row[attribute.Property]);
                        }
                        else if (info.PropertyType.Equals(typeof(DateTime)))
                        {
                            value = Convert.ToDateTime(row[attribute.Property]);
                        }
                        else if (info.PropertyType.Equals(typeof(double)))
                        {
                            value = Convert.ToDouble(row[attribute.Property]);
                        }
                        else if (info.PropertyType.Equals(typeof(bool)))
                        {
                            value = Convert.ToBoolean(row[attribute.Property]);
                        }
                        ///利用反射自动将value赋值给obj的相应公共属性
                        info.SetValue(obj, value, null);
                    }
                }
            }
        }
    }

    #endregion
}