C#自定义特性实例

Create Table Dept(  
    deptNo int identity(1,1) primary key,  
    dname nvarchar(10) not null,  
    description nvarchar(100)  
)  
Go  
-- 何问起 hovertree.com 

/**************自定义特性类*****************/ /// <summary> /// 作用：用来说明表名是什么 /// AttributeUsage:说明特性的目标元素是什么 /// AttributeTargets.Class：代表目标元素为Class /// </summary> [AttributeUsage(AttributeTargets.Class)] public class TableAttribute : Attribute{ /// <summary> /// 表名 /// </summary> public string TableName { get; set; } #region 构造方法，可选的 public TableAttribute() { } public TableAttribute(string tableName) { this.TableName = tableName; } #endregion  } /**************自定义特性类*****************/ /// <summary> /// 作用：说明列是否为自动增长列 /// </summary> [AttributeUsage(AttributeTargets.Property)] class IdentityAttribute: Attribute { /// <summary> /// true:是; false:否 /// </summary> public bool IsIdentity { get; set; } } /****************实体类***************/ /// <summary> /// 有意将类名定义成与表名不一致 /// 用Table特性来说明实体类对应的表名是什么 /// </summary> [Table(TableName = "Dept")] public class Department { /// <summary> /// 部门编号，用特性标注为自动增长 /// </summary> [Identity(IsIdentity=true)] public int DeptNo { get; set; } /// <summary> /// 部门名称 /// </summary> public string Dname { get; set; } /// <summary> /// 部门描述 /// </summary> public string Description { get; set; } public Department( string name, string desc) { Dname = name; Description = desc; } } /****************执行持久化操作类***************/ /// <summary> /// 执行持久化操作类 /// </summary> public class ADOManager { /// <summary> /// 将对象的属性值作为表中对应列的值来添加 /// </summary> /// <param name="obj">要添加的对象</param> public int Save(Object obj) { //1.取得类名：代表表名,用到反射  string tableName = obj.GetType().Name; //如果类有TableAttribute特性，在采用特性说明的类名  TableAttribute attr = Attribute.GetCustomAttribute(obj.GetType(), typeof(TableAttribute)) as TableAttribute; if (attr != null) {//说明类加了Table特性  tableName = attr.TableName;//取得表名   } //sql语句模板：insert into Dept(deptno,dname,description) values('2','','');  StringBuilder sql = new StringBuilder("insert into "); sql.Append(tableName); sql.Append(" ("); //循环对象的属性名：取得列名  foreach (PropertyInfo item in obj.GetType().GetProperties()) { //取得是否有自动增长的特性  IdentityAttribute att = Attribute.GetCustomAttribute(item, typeof(IdentityAttribute)) as IdentityAttribute; if (att == null || !att.IsIdentity) {//没有，则添加列   sql.Append(item.Name); sql.Append(","); } } //去除最后一个逗号'  sql.Remove(sql.Length - 1, 1); sql.Append(") values("); //循环取出对象的属性值:为列赋值  foreach (PropertyInfo item in obj.GetType().GetProperties()) { //取得是否有自动增长的特性  IdentityAttribute att = Attribute.GetCustomAttribute(item, typeof(IdentityAttribute)) as IdentityAttribute; if (att == null) {//没有，则追加列的值 //GetValue():obj代表什么对象，null代表没有参数  sql.Append("'" + item.GetValue(obj, null) + "'"); sql.Append(","); } } //去除最后一个逗号'  sql.Remove(sql.Length - 1, 1); sql.Append(")"); //查看完整的sql语句   Console.WriteLine(sql.ToString()); //执行sql语句  SqlConnection conn = new SqlConnection("server=.;database=test;integrated security=true"); SqlCommand comm = new SqlCommand(sql.ToString(), conn); conn.Open(); int r = comm.ExecuteNonQuery(); conn.Close(); return r;//返回执行结果   } } /* 何问起 hovertree.com */ /****************测试类关键代码***************/ Department dept = new Department("开发部", "负责产品的研发"); ADOManager manager = new ADOManager(); int r = manager.Save(dept); Console.WriteLine(r==0?"失败":"成功");