本文介绍的菜单控件采用的css 和ul list来显示菜单，生成的html小，无需javascript支持，对大部分的浏览器都支持，除ie6要单独修改css也可以使其支持。
通过本文可以了解asp.net 控件的开发，及Composite设计模式的实际运用。
采用Composite设计模式设计菜单类：
MenuCompositeitem类
代码如下:

namespace Ruinet.Controls 
{ 
[Serializable()] 
public class MenuCompositeItem 
{ 
private List<MenuCompositeItem> _children = new List<MenuCompositeItem>(); 
private string _text; 
private string _link; 
private string _target; 
/// <summary> 
/// 菜单项 
/// </summary> 
/// <param name="text">菜单名</param> 
/// <param name="link">链接</param> 
public MenuCompositeItem(string text, string link) 
{ 
this._text = text; 
this._link = link; 
} 
/// <summary> 
/// 菜单项 
/// </summary> 
/// <param name="text">菜单名</param> 
/// <param name="link">链接</param> 
/// <param name="target">跳转目标</param> 
public MenuCompositeItem(string text, string link, string target) 
{ 
this._text = text; 
this._link = link; 
this._target = target; 
} 
/// <summary> 
/// 设置或获取菜单名 
/// </summary> 
public string Text 
{ 
get { return _text; } 
set { _text = value; } 
} 
/// <summary> 
/// 设置或获取链接 
/// </summary> 
public string Link 
{ 
get { return _link; } 
set { _link = value; } 
} 
/// <summary> 
/// 跳转目标 
/// </summary> 
public string Target 
{ 
get { return _target; } 
set { _target=value; } 
} 
/// <summary> 
/// 设置或获取子菜单 
/// </summary> 
public List<MenuCompositeItem> Children 
{ 
get { return _children; } 
set { _children = value; } 
} 
} 
 
MenuComposite类 
 代码如下:

namespace Ruinet.Controls 
{ 
[DefaultProperty("Menu")] 
[ToolboxData("<{0}:MenuComposite runat=server></{0}:MenuComposite>")] 
public class MenuComposite : WebControl 
{ 
/// <summary> 
/// 设置获取选择的菜单 
/// </summary> 
[Bindable(true)] 
[DefaultValue("")] 
[Localizable(true)] 
public string SelectedMenuText 
{ 
get 
{ 
String s = (String)ViewState["SelectedMenuText"]; 
return ((s == null) ? String.Empty : s); 
} 
set 
{ 
ViewState["SelectedMenuText"] = value; 
} 
} 
/// <summary> 
/// 获取和设置菜单项从ViewState 
/// </summary> 
[Bindable(true)] 
[DefaultValue(null)] 
[Localizable(true)] 
public MenuCompositeItem MenuItems 
{ 
get 
{ 
return ViewState["MenuItems"] as MenuCompositeItem; 
} 
set 
{ 
ViewState["MenuItems"] = value; 
} 
} 
/// <summary> 
/// 呈现菜单结构 
/// </summary> 
/// <param name="output">HTML
输出流</param> 
protected override void RenderContents(HtmlTextWriter output) 
{ 
MenuCompositeItem root = this.MenuItems; 
output.Write(@"<div class=""navmenu"">"); 
output.Write(@" <ul>"); 
for (int i = 0; i < root.Children.Count; i++) 
{ 
RecursiveRender(output, root.Children[i]); 
} 
output.Write(@" </ul>"); 
output.Write(@"</div>"); 
} 
/// <summary> 
/// 递归

输出菜单项
/// </summary>
/// <param name="output">HTML输出流</param>
/// <param name="item">菜单项.</param>
/// <param name="depth">Indentation depth.</param>
private void RecursiveRender(HtmlTextWriter output, MenuCompositeItem item)
{
output.Write("<li>");
if (string.IsNullOrEmpty(item.Target))//为空不设置跳转目标
{
output.Write(@"<a href=""" + item.Link + @""">");
}
else
{
output.Write(@"<a href=""" + item.Link + @""" target= """ + item.Target + @""">");
}
if (item.Text == SelectedMenuText) //选中的菜单
{
output.Write(@"<span class=""selected"">");
output.WriteLine(item.Text);
output.WriteLine("</span>");
}
else
{
output.Write(item.Text);
}
output.Write("</a>");
if (item.Children.Count > 0)
{
output.WriteLine();
output.Write("<ul>");
for (int i = 0; i < item.Children.Count; i++)
{
RecursiveRender(output, item.Children[i]);
}
output.Write("</ul>");
}
output.Write("</li>");
}
}
}

在页面中使用
添加对控件的引用后就可以直接在“工具箱”-》Controls组件中 看到MenuComposite组件
再就可以像其他asp.net 控件一样使用
使用：
代码如下:

MenuCompositeItem root = new MenuCompositeItem("root", null); 
MenuCompositeItem menu01 = new MenuCompositeItem("menu01", ResolveUrl("~/Default.aspx")); 
MenuCompositeItem menu02 = new MenuCompositeItem("menu02", ResolveUrl("~/Default.aspx")); 
MenuCompositeItem menu03 = new MenuCompositeItem("menu03", ResolveUrl("~/Default.aspx")); 
MenuCompositeItem menu04 = new MenuCompositeItem("menu04", ResolveUrl("~/Page04.aspx")); 
MenuCompositeItem menu05 = new MenuCompositeItem("menu05", ResolveUrl("~/Default.aspx")); 
MenuCompositeItem menu01_01 = new MenuCompositeItem("menu01-01", ResolveUrl("~/Default.aspx")); 
MenuCompositeItem menu01_02 = new MenuCompositeItem("menu01-02", ResolveUrl("~/Page01-02.aspx")); 
MenuCompositeItem menu01_03 = new MenuCompositeItem("menu01-03", ResolveUrl("~/Default.aspx")); 
MenuCompositeItem menu01_04 = new MenuCompositeItem("menu01-04", ResolveUrl("~/Default.aspx")); 
menu01.Children.Add(menu01_01); 
menu01.Children.Add(menu01_02); 
menu01.Children.Add(menu01_03); 
menu01.Children.Add(menu01_04); 
MenuCompositeItem menu02_01 = new MenuCompositeItem("menu02-01", ResolveUrl("~/Default.aspx")); 
MenuCompositeItem menu02_02 = new MenuCompositeItem("menu02-02", ResolveUrl("~/Default.aspx"), "menu02-02"); 
menu02.Children.Add(menu02_01); 
menu02.Children.Add(menu02_02); 
MenuCompositeItem menu04_01 = new MenuCompositeItem("menu04-01", ResolveUrl("~/Default.aspx")); 
MenuCompositeItem menu04_02 = new MenuCompositeItem("menu04-02", ResolveUrl("~/Page04-02.aspx"), "_blank"); 
menu04.Children.Add(menu04_01); 
menu04.Children.Add(menu04_02); 
root.Children.Add(menu01); 
root.Children.Add(menu02); 
root.Children.Add(menu03); 
root.Children.Add(menu04); 
root.Children.Add(menu05); 
 
TheMenuComposite.MenuItems = root; 
此时生成的编译运行后会生成一个没有样式Ul list ,效果如下： 
  
因此要生成可显示和隐藏的菜单项，关键在css的设置上，开始时将二级子菜单设置为隐藏visibility: hidden; 
同时定义li的hover事件，li:hover时：自菜单的 visibility要改为visible; 大致原理是这样，当然还有注意菜单项的位置 
一级菜单float:left;使其能水平显示。 
CSS定义如下： 
 代码如下:

.navmenu * 
{ 
margin: 0; 
padding: 0; 
} 
.navmenu 
{ 
border: #000 1px solid; 
height: 25px; 
} 
.navmenu li 
{ 
/*水平菜单*/ 
float: left; 
list-style: none; 
position: relative; 
} 
.navmenu a 
{ 
display: block; 
font-size: 12px; 
height: 24px; 
width: 100px; 
line-height: 24px; 
background-color: #CDEB8B; 
color: #0000ff; 
text-decoration: none; 
text-align: center; 
border-left: #36393D 1px inset; 
border-right: #36393D 1px inset; 
border-bottom: #36393D 1px inset; 
} 
/*单独设置一级菜单样式*/ 
.navmenu > ul > li > a 
{ 
font-size: 11px; 
font-weight: bold; 
} 
.navmenu a:hover 
{ 
background: #369; 
color: #fff; 
} 
/*新增的二级菜单部分*/ 
.navmenu ul ul 
{ 
visibility: hidden; /*开始时是隐藏的*/ 
position: absolute; 
left: 0px; 
top: 24px; 
} 
.navmenu ul li:hover ul, .navmenu ul a:hover ul 
{ 
visibility: visible; 
} 
.navmenu ul ul li 
{ 
clear: both; /*垂直显示*/ 
text-align: left; 
} 
/*选中菜单项*/ 
.navmenu .selected 
{ 
padding-left:15px; 
background-position-x:0px; 
background-image: url(./res/selected.gif); 
background-repeat: no-repeat; 
text-decoration:underline; 
} 
 
定义CSS后的效果如下： 

到此菜单控件已完成。已测试过可以在IE7,IE8,Chrome,Firefox中正常显示，在IE6显示可能会有问题，可以参考纯CSS多级菜单 进行修改， 
本文的CSS显示部分参考了此文的介绍。 
附上完整代码，如需要可自行下载修改 下载文件
 
 




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