手把手教你做下拉菜单[龙族首发][本人独创ajax下拉菜单][多个社区加为精华] - 编程论坛

手把手教你做下拉菜单[龙族首发][本人独创ajax下拉菜单]
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_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;
}

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

/// <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;
}

}