反射创建对象

一、理论实例

1、动态载入DLL创建对象

                var assembly = Assembly.LoadFrom("C:\\Binn\\Sample.dll");
                var t = assembly.GetType("Sample.Report");
                var report = (IReport)Activator.CreateInstance(t);

2、判断对象是否继承于某接口

            Type t = typeof(ClsA).GetInterface("IB");
            Console.Write(t==null);

二、应用场景

多库支持：一个程序的数据保存在两个库中，希望根据参数动态的创建数据库对象；

1、我们首先实现一个数据库接口

    public interface IDatabase
    {
        DataTable Execute(string sql);
    }

2、创建继承该接口的数据库类

    public class ArchiveDB : IDatabase
    {
        public DataTable Execute(string sql)
        {
            DataTable dt;
            var db = new SQLServer2000 {ConnStr = Blackice.Config.WebConfig.ArchiveDB};
            db.Execute(sql, out dt);
            return dt;
        }
    }

    public class CurrentDB :IDatabase
    {
        public DataTable Execute(string sql)
        {
            DataTable dt;
            var db = new SQLServer2000 { ConnStr = Blackice.Config.WebConfig.CurrentDB };
            db.Execute(sql, out dt);
            return dt;
        }
    }

3、获取数据的示例

        /// <summary>
        /// 获取数据
        /// </summary>
        /// <param name="dbname">指定的数据库名称</param>
        /// <param name="condition">查询条件</param>
        /// <returns></returns>
        public DataTable GetDataTable(string dbname,string tableName, string condition)
        {
            //根据指定的dbname反射创建数据访问接口
            var assembly = Assembly.LoadFrom(string.Format("{0}\\SqlHelper.dll", Blackice.Config.WebConfig.BinnPath));
            var typeName = string.Format("SqlHelper.{0}", dbname);
            var t = assembly.GetType(typeName);
            var db = (IDatabase)Activator.CreateInstance(t);

            //获取数据
            var dt = db.Execute(string.Format("select * from {0} where prtNum='{1}'",tableName, condition));
            return dt;
        }