手把手教你做下拉菜单篇

此文章由本人以爱像深蓝3313576 首发于龙族社区,如需转载请注明出处!

市面上讲述下拉菜单的文章多如牛毛,且使用下拉菜单的网站也非常之多,但在下看来,90%的网站和教程使用了如下代码:
 function MM_reloadPage(init) {  //reloads the window if Nav4 resized
  if (init==true) with (navigator) {if ((appName=="Netscape")&&(parseInt(appVersion)==4)) {
    document.MM_pgW=innerWidth; document.MM_pgH=innerHeight; onresize=MM_reloadPage; }}
  else if (innerWidth!=document.MM_pgW || innerHeight!=document.MM_pgH) location.reload();
}
MM_reloadPage(true);
// -->

function MM_findObj(n, d) { //v4.0
  var p,i,x;  if(!d) d=document; if((p=n.indexOf("?"))>0&&parent.frames.length) {
    d=parent.frames[n.substring(p+1)].document; n=n.substring(0,p);}
  if(!(x=d[n])&&d.all) x=d.all[n]; for (i=0;!x&&i<d.forms.length;i++) x=d.forms[i][n];
  for(i=0;!x&&d.layers&&i<d.layers.length;i++) x=MM_findObj(n,d.layers[i].document);
  if(!x && document.getElementById) x=document.getElementById(n); return x;
}

function MM_showHideLayers() { //v3.0
  var i,p,v,obj,args=MM_showHideLayers.arguments;
  for (i=0; i<(args.length-2); i+=3) if ((obj=MM_findObj(args[i]))!=null) { v=args[i+2];
    if (obj.style) { obj=obj.style; v=(v=='show')?'visible':(v='hide')?'hidden':v; }
    obj.visibility=v; }
}

在下因公司的一个项目需要学习完ajax这个最流行的web技术之后,独辟蹊径想出一个集完全无刷新实时更新的下拉菜单,而且这个下拉菜单可以无限的可扩展性.下面请看源码:
1.数据库,为了方便大家下载,在下所使用的是access,即想学习的朋友可以直接下载我包含数据库mdb文件的rar包,解压至IIS的发布目录即可直接查看效果.
2.表结构如下图:

3.在下使用的是最传统的两层结构:
数据库连接层DAL,Model数据模型层
DAL  db.cs源码:
using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Data.OleDb;
using System.IO;

/// <summary>
/// DB 的摘要说明
/// </summary>
public class DB
{
    private string strConn = System.Configuration.ConfigurationSettings.AppSettings["strConn"] + AppDomain.CurrentDomain.BaseDirectory + System.Configuration.ConfigurationSettings.AppSettings["strDBPath"];
    private OleDbConnection cn = null;
    public DB()
    {
        try
        {
            cn = new OleDbConnection(strConn);
        }
        catch (OleDbException oe)
        {
            Console.Write(oe.Message);
        }
    }

    /// <summary>
    /// 通过Sql脚本执行数据库增,删,改操作
    /// </summary>
    /// <param name="strSql">Sql脚本</param>
    /// <returns>true表示执行成功,false表示执行失败</returns>
    public bool ExecCmdBySql(string strSql)
    {
        bool foo = true;

        try
        {
            cn.Open();
            OleDbCommand cmd = new OleDbCommand();
            cmd.CommandText = strSql;
            cmd.Connection = cn;
            cmd.ExecuteNonQuery();
        }
        catch (OleDbException oe)
        {
            foo = false;
            Console.Write(oe.Message);
        }
        finally
        {
            cn.Close();//关闭接连
        }

        return foo;
   
    }

   
    /// <summary>
    /// 通过查询得到数据集
    /// </summary>
    /// <param name="strSql">查询Sql脚本</param>
    /// <param name="ds">数据集引用</param>
    /// <param name="tableName">表名</param>
    /// <returns>true表示成功查询得到数据集,false表示查询失败</returns>
    public bool GetDataSetByQuery(string strSql,ref DataSet ds,string tableName)
    {
        bool foo = true;
        try
        {
            cn.Open();
            OleDbCommand cmd = new OleDbCommand();
            cmd.CommandText = strSql;
            cmd.Connection = cn;
            OleDbDataReader reader = cmd.ExecuteReader();
            ds.Load(reader, LoadOption.OverwriteChanges, new string[] { tableName });
        }
        catch (OleDbException oe)
        {
            foo = false;
            Console.Write(oe.Message);
        }
        finally
        {
            cn.Close();
        }

        return foo;
    }

    /// <summary>
    /// 通过查询得到首行数据编号
    /// </summary>
    /// <param name="strSql">Sql脚本</param>
    /// <param name="id">编号</param>
    /// <returns></returns>
    public bool GetScalarByQuery(string strSql, ref long id)
    {
        bool foo = true;
        try
        {
            cn.Open();
            OleDbCommand cmd = new OleDbCommand();
            cmd.CommandText = strSql;
            cmd.Connection = cn;
            Object obj = cmd.ExecuteScalar();
            if (!obj.ToString().Equals(""))
            {
                id = (long)obj;
            }
            else
            {
                id = 1;
            }
        }
        catch (OleDbException oe)
        {
            foo = false;
            Console.Write(oe.Message);
        }
        finally
        {
            cn.Close();
        }

        return foo;
    }

}

注:只考虑access数据库Sql连接的情况故有三个方法;

model层: CMenu类

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;

/// <summary>
/// CMenu 的摘要说明
/// </summary>
public class CMenu
{
    private long menu_id; //菜单编号
    private string menu_name;//菜单名称
    private long menu_parentID;//父级菜单编号
    public long Menu_id
    {
        get { return menu_id; }
        set { menu_id = value; }
    }
    public string Menu_name
    {
        get { return menu_name; }
        set { menu_name = value; }
    }
    public long Menu_parentID
    {
        get { return menu_parentID; }
        set { menu_parentID = value; }
    }
    public CMenu()
 {
        menu_id = -1; //菜单编号
        menu_name = "";//菜单名称
        menu_parentID = -1;//父级菜单编号
 }

    /// <summary>
    /// 得到当前记录应该插入的编号
    /// </summary>
    /// <returns>true表示执行成功,false表示执行失败</returns>
    public bool GetID()
    {
        bool foo = false;
       
        DB db = new DB();

        string strSql = "select max(menu_id) from menu";


        if (db.GetScalarByQuery(strSql, ref menu_id))
        {
            foo = true;
        }

        return foo;
    }

    public bool Insert2DB()
    {
        bool foo = false;

        if (!GetID())
        {
            return foo;
        }

        string strSql = "insert into menu ";
        string strAttribute = " (menu_id";
        string strValue = " (" + menu_id;

        if (!menu_name.Equals(""))
        {
            strAttribute += " ,menu_name";
            strValue += ",'" + menu_name + "'";
        }

        if (-1 != menu_parentID)
        {
            strAttribute += " ,menu_parentID";
            strValue += "," + menu_parentID;
        }

        strAttribute += ")";
        strValue += ")";
        strSql += strAttribute + strValue;

        DB db = new DB();

        if (db.ExecCmdBySql(strSql))
        {
            foo = true;
        }

        return foo;
    }

    public bool Delete2DB()
    {
        bool foo = false;

        string strSql = "delete from menu where menu_id = " + menu_id;

        DB db = new DB();

        if (db.ExecCmdBySql(strSql))
        {
            foo = true;
        }

        return foo;
    }

    public bool Delete2DB(string strConn)
    {
        bool foo = false;

        string strSql = "delete from menu " + strConn;

        DB db = new DB();

        if (db.ExecCmdBySql(strSql))
        {
            foo = true;
        }

        return foo;

    }

    public bool Update2DB()
    {
        bool foo = false;

        string strSql = "update menu set menu_id = menu_id ";

        if (!menu_name.Equals(""))
        {
            strSql += " menu_name = '" + menu_name + "'";
        }

        if (-1 != menu_parentID)
        {
            strSql += " menu_parentID = " + menu_parentID;
        }

        strSql += " where menu_id =" + menu_id ;

        DB db = new DB();

        if (db.ExecCmdBySql(strSql))
        {
            foo = true;
        }

        return foo;
    }

    public bool Query2DB(ref DataSet ds,string strColunm ,string strConn)
    {
        bool foo = false;

        string strSql = "select * from ";

        if (!strColunm.Equals(""))
        {
            strSql ="select " + strColunm + " from menu ";
        }

        if (!strConn.Equals(""))
        {
            strSql += strConn;
        }

        DB db = new DB();

        if (db.GetDataSetByQuery(strSql, ref ds, "menu"))
        {
            foo = true;
        }

        return foo;
    }

}

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原文地址：https://www.cnblogs.com/shinefzh/p/1129804.html