技术资料 > .Net专区 > winform应用 : 从一个舆论调查的制作谈面向对象的编程思路（二）

从一个舆论调查的制作谈面向对象的编程思路（二）

March 25,2004

首先，我们要来定义一个数据库表，以保存舆论调查的想关数据，看下面这个表：
/*新闻调查表*/
if exists(select * from sysobjects where id = object_id('Survey'))
drop table Survey
go

create table Survey
(
  ID       int       identity Primary key not null ,
  SurveyID varchar(20) default ""       not null ,
  Kind       tinyint       default 0       not null ,
  Title       nvarchar(100) default ""       not null ,
  Description nvarchar(255) default ""       not null ,
  Amount int       default 0       not null ,
  BeginTime datetime default getdate() not null ,
  EndTime datetime default getdate() not null ,
  Active bit       default 0       not null
)
go

好了，数据库建好了，我可以从上面的survey基类中继承出具体的子类，比如说我现在要做一个同足球相

关的调查，那就做这么一个类：

namespace Football
{
using System;
using MyClass.Util ;
using System.Data.SQL ;
using System.Collections ;
/// <summary>
/// 足球舆论调查
/// </summary>
/// <remarks>
/// 从MyClass.Util.Survey类继承而来
/// </remarks>
public class FootballSurvey : MyClass.Util.Survey
{

      public FootballSurvey()
      {
      }

      /// <summary>
      /// 重载父类虚函数
      /// </summary>
      /// <param name="a_intID">该调查的数据库id </param>
      public override void LoadFromDatabase(string a_strID)
      {
         MyClass.Util.MyConnection myConn = new MyConnection() ;
         SQLCommand myCommand = new SQLCommand() ;
         myCommand.CommandText = "up_GetSurvey" ;
         myCommand.CommandType = System.Data.CommandType.StoredProcedure ;

         try
         {
            myConn.Open() ;
            myCommand.ActiveConnection = myConn ;
            myCommand.Parameters.Add(new SQLParameter("@a_strsurveyid" ,

SQLDataType.VarChar , 20)) ;
            myCommand.Parameters["@a_strsurveyid"].Value = a_strID ;
            SQLDataReader myReader ;
            myCommand.Execute(out myReader) ;

            //先取调查
            if (myReader.Read())
            {
                  this.m_strTitle = myReader["title"].ToString() ;
                  this.m_intHits = (int)myReader["amount"] ;
                  this.m_strID = a_strID ;
                  this.m_datBeginTime =

(DateTime)myReader["begintime"] ;
                  this.m_datEndTime = (DateTime)myReader["endtime"] ;
            }
            else
            {
                  throw(new Exception("数据库中无此调查的纪录")) ;
            }

            //清空调查项
            m_arrItems.Clear() ;

            //取调查项
            if (myReader.HasMoreRows)
            {
                  while(myReader.Read())
                  {
                     SurveyItem item = new SurveyItem() ;
                     item.Text = myReader["title"].ToString() ;
                     item.ID = (int)myReader["id"] ;
                     item.Count = (int)myReader["amount"] ;
                     item.Description =

myReader["Description"].ToString() ;
                     AddItem(item) ;
                  }
            }
            else
            {
                  throw(new Exception("数据库中没有该调查相关的调查项

")) ;
            }

            //清场
            myReader.Close() ;
            myConn.Close() ;
         }
         catch(Exception e)
         {
            throw(new Exception("从数据库中读取调查失败：" +

e.ToString())) ;
         }
      }

      /// <summary>
      /// 将调查保存到数据库
      /// </summary>
      /// <param name="m_strSurveyID">调查编号 </param>
      /// <remarks>
      /// 如果m_strSurveyID不为空，则删除原纪录，用当前调查编号保存新的调查，
      /// 否则就生成一个新的调查编号
      /// </remarks>
      public override void SaveToDatabase(string m_strSurveyID)
      {
         //如果没有标题或调查项则抛出异常
         if (this.m_arrItems.Count == 0 || this.m_strTitle == "")
         {
            throw(new Exception("没有调查标题或标题项")) ;
         }

         MyClass.Util.MyConnection myConn = new MyConnection() ;
         SQLCommand myCommand = new SQLCommand() ;
         myCommand.CommandType = System.Data.CommandType.Text ;

         try
         {
            myConn.Open() ;
            myCommand.ActiveConnection = myConn ;

            //如果没有surveyid则生成surveyid
            string strSurveyID ;
            if(m_strSurveyID == "")
            {
                  strSurveyID = DateTime.Now.Year.ToString()
                              +

DateTime.Now.Month.ToString()
                              +

DateTime.Now.Hour.ToString()
                              +

DateTime.Now.Minute.ToString()
                              +

DateTime.Now.Second.ToString()
                              +

DateTime.Now.Millisecond.ToString() ;
            }
            else //如果已有，则删除该条纪录
            {
                  strSurveyID = m_strSurveyID ;
                  //删除原有纪录
                  myCommand.CommandText = "delete from survey where

surveyid='" + strSurveyID + "'" ;
                  myCommand.ExecuteNonQuery() ;
            }

            string strSql = "insert into survey(surveyid , kind , title)

values ('"
                              + strSurveyID +"', 0 , '" +

m_strTitle + "')rn" ;
            for (int i = 0 ; i < m_arrItems.Count ; i ++)
            {
                  strSql += "insert into survey(surveyid , kind ,

title) values('"
                     + strSurveyID + "' , 1 , '"
                     + ((SurveyItem)m_arrItems).Text +

"')rn" ;
            }
            //插库
            myCommand.CommandText = strSql ;
            myCommand.ExecuteNonQuery() ;

            //清场
            myConn.Close() ;
         }
         catch(Exception e)
         {
            throw(new Exception("保存调查时出错：" +  e.ToString())) ;
         }

      }

      /// <summary>
      /// 投票
      /// </summary>
      /// <param name="a_intID"> </param>
      public override void Vote(int a_intID)
      {
         //该项计数加一
         ((SurveyItem)m_arrItems[a_intID]).Count += 1 ;

         //数据库中改变
         MyConnection myConn = new MyConnection() ;
         SQLCommand myCommand = new SQLCommand() ;
         myCommand.CommandText = "update survey set amount=amount+1 where

id="
                                 +

((SurveyItem)m_arrItems[a_intID]).ID.ToString() ;

         myCommand.CommandType = System.Data.CommandType.Text ;

         try
         {
            myConn.Open() ;
            myCommand.ActiveConnection = myConn ;
            myCommand.ExecuteNonQuery() ;
            myConn.Close() ;
         }
         catch(Exception e)
         {
            throw(new Exception("更新调查项失败:" + e.ToString())) ;
         }

      }

      /// <summary>
      /// 调查列表
      /// </summary>
      public static ArrayList SurveyList()
      {
         ArrayList arrResult = new ArrayList() ;
         MyClass.Util.MyConnection myConn = new MyConnection() ;
         SQLCommand myCommand = new SQLCommand() ;
         myCommand.CommandText = "select id , surveyid , title from survey

where kind=0 order by surveyid desc" ;
         myCommand.CommandType = System.Data.CommandType.Text ;

         try
         {
            myConn.Open() ;
            myCommand.ActiveConnection = myConn ;
            SQLDataReader myReader ;
            myCommand.Execute(out myReader) ;
            while (myReader.Read())
            {
                  FootballSurvey mySurvey = new FootballSurvey() ;
                  mySurvey.Title = myReader["title"].ToString() ;
                  mySurvey.SurveyID = myReader["surveyid"].ToString()

;
                  arrResult.Add(mySurvey) ;
            }

            myReader.Close() ;
            myConn.Close() ;

         }
         catch(Exception e)
         {
            throw(new Exception("从数据库中取出调查失败:" +

e.ToString())) ;
         }

         //返回结果
         return arrResult ;
      }

      /// <summary>
      /// 取得激活的调查id
      /// </summary>
      public static string GetActiveSurveyID()
      {
         string strResult = "" ;

         MyClass.Util.MyConnection myConn = new MyConnection() ;
         SQLCommand myCommand = new SQLCommand() ;
         myCommand.CommandText = "select top 1 id , surveyid from survey

where active=1 order by id desc" ;
         myCommand.CommandType = System.Data.CommandType.Text ;

         try
         {
            myConn.Open() ;
            myCommand.ActiveConnection = myConn ;
            SQLDataReader myReader ;
            myCommand.Execute(out myReader) ;
            if (myReader.Read())
            {
                  strResult = myReader["surveyid"].ToString() ;
            }
            else
            {
                  throw(new Exception("没有激活的调查")) ;
            }

            myReader.Close() ;

         }
         catch(Exception e)
         {
            throw(new Exception("从数据库中取出调查失败:" +

e.ToString())) ;
         }
         finally
         {
            myConn.Close() ;
         }

         //返回结果
         return strResult ;

      }

      /// <summary>
      /// 激活调查
      /// </summary>
      /// <param name="a_strSurveyID">调查编号 </param>
      public static void ActiveSurvey(string a_strSurveyID)
      {
         MyClass.Util.MyConnection myConn = new MyClass.Util.MyConnection() ;
         SQLCommand myCommand = new SQLCommand() ;
         myCommand.CommandText = "update survey set active=0 ;"
                                 + "update survey set

active=1 where surveyid='" + a_strSurveyID + "'" ;
         myCommand.CommandType = System.Data.CommandType.Text ;

         try
         {
            myConn.Open() ;
            myCommand.ActiveConnection = myConn ;
            myCommand.ExecuteNonQuery() ;
         }
         catch(Exception exp)
         {
            throw(new Exception("保存激活调查到数据库出错：" +

exp.ToString()));
         }
         finally
         {
            myConn.Close() ;
         }
      }

}
}