利用反射来做‘历史变更’记录

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有这样一个需求，要求操作数据库时‘留痕’，具体需求如下：

假设操作如下一张表：

create table Student
(
StudentId varchar(100) primary key not null,
StudentName nvarchar(20),--姓名
StudentNo varchar(10),--学号
SutdentSex varchar(1),--性别
ProvinceFrom nvarchar(50),--省份
CityFrom nvarchar(50),--城市
CreateDate datetime default(getdate()),
)

需求如下：当更新学生表时，要求记录如下信息：

create table ChangeHistory
(
HistoryId varchar(100) primary key not null,
ChangeField  nvarchar(50),--所修改字段的中文含义
BeforeChangeValue nvarchar(100),--修改前的值
AfterChangeValue nvarchar(100),--修改后的值
ChangeBy nvarchar(20),--修改人
ChangeTime datetime,--修改时间
)

看到上述两张表，你会不会感觉很简单呢？

可能会有人立马想到一个笨方法，如下：

List<StudentModel> DataBaseStudentList = new List<StudentModel>();//用于模拟数据库学生表中的4条记录
        protected void Page_Load(object sender, EventArgs e)
        {
            //学生一
            StudentModel M1 = new StudentModel()
            {
                StudentId = "01",
                CityFrom = "苏州",
                ProvinceFrom = "江苏",
                StudentName = "啊龙",
                StudentNo = "081309201",
                SutdentSex = "男"
            };
            //学生二
            StudentModel M2 = new StudentModel()
            {
                StudentId = "02",
                CityFrom = "苏州",
                ProvinceFrom = "江苏",
                StudentName = "阿狗",
                StudentNo = "081309202",
                SutdentSex = "男"
            };
            //学生三
            StudentModel M3 = new StudentModel()
            {
                StudentId = "03",
                CityFrom = "苏州",
                ProvinceFrom = "江苏",
                StudentName = "阿猫",
                StudentNo = "081309203",
                SutdentSex = "女"
            };
            //学生四
            StudentModel M4 = new StudentModel()
            {
                StudentId = "04",
                CityFrom = "苏州",
                ProvinceFrom = "江苏",
                StudentName = "阿猪",
                StudentNo = "081309204",
                SutdentSex = "女"
            };
            DataBaseStudentList.Add(M1);
            DataBaseStudentList.Add(M2);
            DataBaseStudentList.Add(M3);
            DataBaseStudentList.Add(M4);
            //数据库填充完后，我们修改学生表
            string StudentId = "03";
            StudentModel ef = DataBaseStudentList.Where(A => A.StudentId == StudentId).FirstOrDefault();
            if (ef != null)
            {
                ef.StudentName = "阿狸猫";//修改了姓名
            }
            //调用历史变更的方法。
            UpdateStudent(ef, StudentId);
        }

        public void UpdateStudent(StudentModel newModel, string StudentId)
        {
            List<ChangeHistoryModel> ChangeHistoryList = new List<ChangeHistoryModel>();
            var oldef = DataBaseStudentList.Where(A => A.StudentId == StudentId).FirstOrDefault();
            if(oldef.CityFrom!= newModel.CityFrom)
            {
                ChangeHistoryModel M = new ChangeHistoryModel()
                {
                    HistoryId = Guid.NewGuid().ToString(),
                    ChangeField = "学生所属城市",
                    BeforeChangeValue = oldef.CityFrom,
                    AfterChangeValue = newModel.CityFrom,
                    ChangeBy = "修改人姓名",
                    ChangeTime = DateTime.Now
                };
            }

            if (oldef.ProvinceFrom != newModel.ProvinceFrom)
            {
                ChangeHistoryModel M = new ChangeHistoryModel()
                {
                    HistoryId = Guid.NewGuid().ToString(),
                    ChangeField = "学生所属省份",
                    BeforeChangeValue = oldef.ProvinceFrom,
                    AfterChangeValue = newModel.ProvinceFrom,
                    ChangeBy = "修改人姓名",
                    ChangeTime = DateTime.Now
                };
            }

            if (oldef.StudentName != newModel.StudentName)
            {
                ChangeHistoryModel M = new ChangeHistoryModel()
                {
                    HistoryId = Guid.NewGuid().ToString(),
                    ChangeField = "学生姓名",
                    BeforeChangeValue = oldef.StudentName,
                    AfterChangeValue = newModel.StudentName,
                    ChangeBy = "修改人姓名",
                    ChangeTime = DateTime.Now
                };
            }
            /*
            ...
            ... 等等其他字段的修改
            ...
            */

            //最后将历史变更插入数据库
        }

上述的方法是通过每个字段作比对，如果不一致，则生成变更记录，这种方法实现了上述要求，但如果有上百个字段，那么...

OK，下面我们用反射结合.config文件来实现！

 1、新建SelectItem.config文件，用来将数据表字段对应中文含义，如下：

<?xml version="1.0" encoding="utf-8"?>
<config>
  <!--学生信息解读 反射案例 历史变更记录-->
  <StudentInfo value="StudentName">学生姓名</StudentInfo>
  <StudentInfo value="StudentNo">学号</StudentInfo>
  <StudentInfo value="SutdentSex">性别</StudentInfo>
  <StudentInfo value="ProvinceFrom">省份</StudentInfo>
  <StudentInfo value="CityFrom">城市</StudentInfo>
</config>

2、创建两个Model，一个OldModel，代表没修改之前的Model，一个NewModel，代表修改后的Model，如下：

    public class StudentOldModel
    {
        public string StudentId { get; set; }
        public string StudentName { get; set; }
        public string StudentNo { get; set; }
        public string SutdentSex { get; set; }
        public string ProvinceFrom { get; set; }
        public string CityFrom { get; set; }
        public string CreateDate { get; set; }
    }

    public class StudentNewModel
    {
        public string StudentId { get; set; }
        public string StudentName { get; set; }
        public string StudentNo { get; set; }
        public string SutdentSex { get; set; }
        public string ProvinceFrom { get; set; }
        public string CityFrom { get; set; }
        public string CreateDate { get; set; }
    }

3、构造老的OldModel，和新的NewModel，如下：

//来自数据库
            StudentOldModel M1 = new StudentOldModel()
            {
                StudentId = "01",
                CityFrom = "苏州",
                ProvinceFrom = "江苏",
                StudentName = "啊龙",
                StudentNo = "081309201",
                SutdentSex = "男"
            };

            //用户修改后
            StudentNewModel M2 = new StudentNewModel()
            {
                StudentId = "01",
                CityFrom = "郑州",
                ProvinceFrom = "河南",
                StudentName = "啊龙",
                StudentNo = "081309201",
                SutdentSex = "男"
            };

4、利用反射结合.config文件记录变更如下：

       public static void UpdateHistory(StudentNewModel newModel, StudentOldModel oldModel, string modifyUserName, string modifyWeb)
        {
            List<ChangeHistoryModel> ChangeHistoryModelList = new List<ChangeHistoryModel>();
            Type t = newModel.GetType();
            PropertyInfo[] PropertyList = t.GetProperties();
            //
            Type tSource = oldModel.GetType();
            PropertyInfo[] SourcePropertyList = tSource.GetProperties();
            var ls = PropertyList.GroupBy(a => a.PropertyType.Name).Select(g => (new { a = g.Key, count = g.Count() })).ToList();
            foreach (PropertyInfo item in PropertyList)
            {
                string name = item.Name;
                string Filed =SelectHelper. GetFiled(name);
                object value = item.GetValue(newModel, null);
                PropertyInfo ef = SourcePropertyList.Where(A => A.Name.ToLower() == name.ToLower()).FirstOrDefault();
                string PropertyType = item.PropertyType.Name;
                if (PropertyType == "String")
                {
                    string ToValue = value == null ? "" : value.ToString();
                    if (ef != null)
                    {
                        object Value2 = ef.GetValue(oldModel, null);
                        string ScoureValue = Value2 == null ? "" : Value2.ToString();
                        if ((ToValue != ScoureValue))
                        {
                            if (!string.IsNullOrEmpty(Filed))
                            {
                                ChangeHistoryModel CM = new ChangeHistoryModel()
                                {
                                    ChangeField = Filed,
                                    BeforeChangeValue = ScoureValue,
                                    AfterChangeValue = ToValue,
                                    HistoryId = Guid.NewGuid().ToString(),
                                    ChangeBy = "修改人姓名",
                                    ChangeTime = DateTime.Now
                                };
                                ChangeHistoryModelList.Add(CM);
                            }
                        }
                    }
                }
            }
        }

上述就可以动态完成变更记录的生成了！需要说明的是：不管数据库字段是什么数据类型，我们要把所有字段转化为Model中的字符串类型String,

需要辅助类如下：

    public class SelectHelper
    {
        private static SelectItemConfig configManager;
        public static Dictionary<string, string> GetConfigByKey(string key, string name = "SelectItem.config")
        {
            string mapPath = HttpContext.Current.Server.MapPath("~/");
            configManager = new SelectItemConfig(mapPath, name);
            Dictionary<string, string> dic = configManager.getItemListByKey(key);
            return dic.OrderBy(p => p.Value).ToDictionary(o => o.Key, p => p.Value); ;
        }

        public static Dictionary<string, string> GetConfigByKeyForFields(string key, string name = "SelectItem.config")
        {
            string mapPath = HttpContext.Current.Server.MapPath("~/");
            configManager = new SelectItemConfig(mapPath, name);
            Dictionary<string, string> dic = configManager.getItemListByKey(key);
            return dic;
        }

        /// <summary>
        /// 获取XML文件中某一节点的值
        /// </summary>
        /// <param name="name"></param>
        /// <returns></returns>
        public static string GetFiled(string name)
        {
            Dictionary<string, string> dic = SelectHelper.GetConfigByKey("StudentInfo");
            string Filed = string.Empty;
            foreach (var item in dic)
            {
                if (item.Key.ToLower() == name.ToLower())
                {
                    Filed = item.Value;
                    break;
                }
            }
            return Filed;
        }
    }

    public class SelectItemConfig
    {
        private XmlDocument _doc;
        private XmlNode _rootNode;

        public SelectItemConfig(String mapPath, string name)
        {
            _doc = new XmlDocument();
            _doc.Load(mapPath + name);
            _rootNode = _doc.DocumentElement;
        }

        public void setConfig(String key, String value)
        {
            if (value == null || (value != null && value.Length == 0)) { return; }

            if (_rootNode.SelectSingleNode(key) == null || (_rootNode.SelectSingleNode(key) != null && _rootNode.SelectSingleNode(key).ChildNodes.Count == 0))
            {
                XmlElement newNode = _doc.CreateElement(key);
                newNode.InnerText = value;
                _rootNode.AppendChild(newNode);
            }
            else
            {
                _rootNode.SelectSingleNode(key).ChildNodes[0].InnerText = value;
            }
        }

        /// <summary>
        /// 获取单个节点的值
        /// </summary>
        /// <param name="key"></param>
        /// <returns></returns>
        public String getConfig(string key)
        {
            if (_rootNode.SelectSingleNode(key) != null)
                if (_rootNode.SelectSingleNode(key).ChildNodes.Count > 0)
                    return _rootNode.SelectSingleNode(key).ChildNodes[0].Value;
                else
                    return "";
            else
                return null;
        }

        /// <summary>
        /// 获取key值对应的多个节点的值的集合
        /// </summary>
        /// <param name="key"></param>
        /// <returns></returns>
        public Dictionary<string, string> getItemListByKey(string key)
        {
            Dictionary<string, string> dic = new Dictionary<string, string>() { };
            if (_rootNode.SelectSingleNode(key) != null)
            {
                XmlNodeList xmlNode = _rootNode.SelectNodes(key);
                int nodeCount = _rootNode.SelectNodes(key).Count;
                if (nodeCount > 0)
                {
                    for (int i = 0; i < nodeCount; i++)
                    {
                        var item = _rootNode.SelectNodes(key).Item(i);
                        dic.Add(item.Attributes["value"].Value, item.InnerText);//Select 下拉框 Value属性
                    }
                }
            }
            return dic;
        }

        public Boolean SaveConfig(String mapPath)
        {
            try
            {
                _doc.Save(mapPath + @"FlexPaper.config");
                return true;
            }
            catch
            {
                return false;
            }
        }
    }

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