Net特性与反射 DEMO

 

对于特性与反射的一些基本知识可以参考MSDN:http://msdn.microsoft.com/zh-cn/library/vstudio/ms173183.aspx

下面利用反射与特性做了一个关于实现DataTable与实体之间的相互转化的Demo.

实体类 Author:

public partial class Author
   {
       public Author()
       { }
       #region Model
       private int _id;
       private string _title;
       private string _content;
       private string _email;
       private string _sex;
       /// <summary>
       ///
       /// </summary>
       [DataFiled("Id", SqlDbType.Int)]
       public int Id
       {
           set { _id = value; }
           get { return _id; }
       }
       /// <summary>
       ///
       /// </summary>
       [DataFiled("Title", SqlDbType.VarChar)]
       public string Title
       {
           set { _title = value; }
           get { return _title; }
       }
       /// <summary>
       ///
       /// </summary>
       [DataFiled("Content", SqlDbType.VarChar)]
       public string Content
       {
           set { _content = value; }
           get { return _content; }
       }
       /// <summary>
       ///
       /// </summary>
       [DataFiled("Email", SqlDbType.VarChar)]
       public string Email
       {
           set { _email = value; }
           get { return _email; }
       }
       /// <summary>
       ///
       /// </summary>
       [DataFiled("Sex", SqlDbType.VarChar)]
       public string Sex
       {
           set { _sex = value; }
           get { return _sex; }
       }
       #endregion Model

   }

自定义特性类DataFiledAttribute和NoDataFiledAttribute类：

[AttributeUsage(AttributeTargets.All, AllowMultiple = true)]
   public class DataFiledAttribute : Attribute
   {
       private string name;
       private SqlDbType paramType;
       private int size;
       /// <summary>
       ///
       /// </summary>
       public string FieldName
       {
           get { return this.name == null ? string.Empty : this.name; }
           set { this.name = value; }
       }

       public SqlDbType SqlDbType
       {
           get { return this.paramType; }
           set { this.paramType = value; }
       }

       public int Size
       {
           get { return this.size; }
           set { this.size = value; }
       }

       public bool IsSizeDefined
       {
           get { return size != 0; }
       }

       public DataFiledAttribute(string strFieldName, SqlDbType sdtSqlDbType, int iSize)
       {
           this.name = strFieldName;
           this.paramType = sdtSqlDbType;
           this.size = iSize;
       }

       public DataFiledAttribute(string strFieldName, SqlDbType sdtSqlDbType)
           : this(strFieldName, sdtSqlDbType, 0)
       {

       }

   }
   [AttributeUsage(AttributeTargets.All, AllowMultiple = true)]
   public class NoDataFiledAttribute : Attribute { }

下面的是实现转化的类了

public class ModelHandler<T>
    {
        /// <summary>
        /// 实体列表转为DataTable 注意：使用本方法，须要实体中的每个属性必须添加DataFieldAttribute特性
        /// </summary>
        /// <param name="objlist">实体列表</param>
        /// <returns>返回DataTable</returns>
        public static System.Data.DataTable Model2DataTable(List<T> objlist)
        {
            if (objlist.Count == 0) return null;
            DataTable dt = GeneratorDataTable(typeof(T));
            foreach (T obj in objlist)
            {
                Type modelType = obj.GetType();
                PropertyInfo[] properties = modelType.GetProperties();
                DataRow dr = dt.NewRow();
                for (int i = 0; i < properties.Length; i++)
                {
                    dr[i] = properties[i].GetGetMethod().Invoke(obj, null);
                }
                dt.Rows.Add(dr);
            }
            return dt;
        }
        private static DataTable GeneratorDataTable(Type modelType)
        {
            //Type modelType = obj.GetType();
            PropertyInfo[] properties = modelType.GetProperties();
            DataFiledAttribute d = null;
            DataTable dt = new DataTable();
            for (int i = 0; i < properties.Length; i++)
            {
                DataColumn dc = new DataColumn();
                d = Attribute.GetCustomAttribute(properties[i], typeof(DataFiledAttribute)) as DataFiledAttribute;
                dc.ColumnName = d.FieldName;
                dc.DataType = typeof(string);
                dt.Columns.Add(dc);

            }
            return dt;
        }
        /// <summary>
        /// DataTable转为实体列表
        /// </summary>
        /// <param name="dt"></param>
        /// <returns></returns>
        public static List<T> DataTable2Model(DataTable dt)
        {
            if (dt.Rows.Count == 0)
            {
                return null;
            }
            List<T> list = new List<T>();

            foreach (DataRow dr in dt.Rows)
            {
                T obj = Activator.CreateInstance<T>();
                foreach (DataColumn dc in dt.Columns)
                {
                    PropertyInfo info = obj.GetType().GetProperty(dc.ColumnName);
                    Type t = info.PropertyType;
                    info.SetValue(obj, Convert.ChangeType(dr[dc], t), null);
                }
                list.Add(obj);
            }
            return list;

        }
    }

具体实现如下：

Author model = new Author();
            model.Id = 1;
            model.Title = "test";
            model.Content = null;
            List<Author> list = new List<Author>();
            list.Add(model);
            DataTable dt = ModelHandler<Author>.Model2DataTable(list);
            List<Author> list1 = new List<Author>();
            list1 = ModelHandler<Author>.DataTable2Model(dt);

查看一下结果：

   DataTable：

  list<model>: