发布一款层次下拉列表控件

在项目中经常遇到树状结构的对象比如产品分类、部门结构、地区……对于这类对象的呈现，一般都使用树控件（比如VS2005自带的TreeView控件）。但是树控件的使用和操作都比较复杂，对于一些比较简单的操作，比如单选其中的一个节点的情况则可用使用下拉列表框来代替。要在DropDownList中展示出树结构的层次，那就必须在每个节点的Text前加入一定的占位符，以实现层次的效果，比如：

由于这种下拉列表控件在项目中经常使用，于是决定写一个通用的服务器控件出来。该控件继承自DropDownList，在使用中只需要为该控件设置用于数据绑定的DataTextField和DataValueField，以及新增的属性ChildProperty（string，对象的Child属性的名字）和DeepChar（string，在表示层次中使用的占位符，默认是“--”），设置了这4个属性后，在后台就只需要将树结构对象的Root节点作为DataSource，然后执行DataBind()即可。

<div style="border-right: #cccccc 1px solid; padding-right: 5px; border-top: #cccccc 1px solid; padding-left: 4px; font-size: 13px; padding-bottom: 4px; border-left: #cccccc 1px solid; width: 98%; word-break: break-all; padding-top: 4px; border-bottom: #cccccc 1px solid; background-color: #eeeeee">
<img id="Code_Closed_Image_104722" onclick="code_collapse_toggle(this);" height="16" alt="" src="/Images/OutliningIndicators/ContractedBlock.gif" width="11" align="top"><img id="Code_Open_Image_104722" style="display: none" onclick="code_collapse_toggle(this);" height="16" alt="" src="/Images/OutliningIndicators/ExpandedBlockStart.gif" width="11" align="top"><span id="Code_Closed_Text_104722" style="border-right: #808080 1px solid; border-top: #808080 1px solid; border-left: #808080 1px solid; border-bottom: #808080 1px solid; background-color: #ffffff">控件Code<span id="Code_Open_Text_104722" style="display: none"><img alt="" src="/Images/OutliningIndicators/None.gif" align="top"><span style="color: #0000ff">using<span style="color: #000000">?System;<img alt="" src="/Images/OutliningIndicators/None.gif" align="top"><span style="color: #0000ff">using<span style="color: #000000">?System.Collections.Generic;<img alt="" src="/Images/OutliningIndicators/None.gif" align="top"><span style="color: #0000ff">using<span style="color: #000000">?System.Collections;<img alt="" src="/Images/OutliningIndicators/None.gif" align="top"><span style="color: #0000ff">using<span style="color: #000000">?System.ComponentModel;<img alt="" src="/Images/OutliningIndicators/None.gif" align="top"><span style="color: #0000ff">using<span style="color: #000000">?System.Linq;<img alt="" src="/Images/OutliningIndicators/None.gif" align="top"><span style="color: #0000ff">using<span style="color: #000000">?System.Text;<img alt="" src="/Images/OutliningIndicators/None.gif" align="top"><span style="color: #0000ff">using<span style="color: #000000">?System.Web;<img alt="" src="/Images/OutliningIndicators/None.gif" align="top"><span style="color: #0000ff">using<span style="color: #000000">?System.Web.UI;<img alt="" src="/Images/OutliningIndicators/None.gif" align="top"><span style="color: #0000ff">using<span style="color: #000000">?System.Web.UI.WebControls;?<img alt="" src="/Images/OutliningIndicators/None.gif" align="top"><img alt="" src="/Images/OutliningIndicators/None.gif" align="top"><span style="color: #0000ff">namespace<span style="color: #000000">?ServerControls<img id="Codehighlighter1_240_3766_Open_Image" onclick="code_collapse_toggle(this);" alt="" src="/Images/OutliningIndicators/ExpandedBlockStart.gif" align="top"><img id="Codehighlighter1_240_3766_Closed_Image" style="display: none" onclick="code_collapse_toggle(this);" alt="" src="/Images/OutliningIndicators/ContractedBlock.gif" align="top"><span id="Codehighlighter1_240_3766_Closed_Text" style="border-right: #808080 1px solid; border-top: #808080 1px solid; display: none; border-left: #808080 1px solid; border-bottom: #808080 1px solid; background-color: #ffffff"><img alt="" src="https://www.52php.cn/res/2019/02-14/22/a76e9bb6ed00cf1c9c9f4ee2f04b558b.gif"&gt;<span id="Codehighlighter1_240_3766_Open_Text"><span style="color: #000000">{<img alt="" src="/Images/OutliningIndicators/InBlock.gif" align="top">????[ToolboxData(<span style="color: #800000">"<span style="color: #800000"><{0}:DropDownTreeList?runat=server></{0}:DropDownTreeList><span style="color: #800000">"<span style="color: #000000">)]<img alt="" src="/Images/OutliningIndicators/InBlock.gif" align="top">????<span style="color: #0000ff">public<span style="color: #000000">?<span style="color: #0000ff">class<span style="color: #000000">?DropDownTreeList?:?DropDownList<img id="Codehighlighter1_375_3764_Open_Image" onclick="code_collapse_toggle(this);" alt="" src="/Images/OutliningIndicators/ExpandedSubBlockStart.gif" align="top"><img id="Codehighlighter1_375_3764_Closed_Image" style="display: none" onclick="code_collapse_toggle(this);" alt="" src="/Images/OutliningIndicators/ContractedSubBlock.gif" align="top">????<span id="Codehighlighter1_375_3764_Closed_Text" style="border-right: #808080 1px solid; border-top: #808080 1px solid; display: none; border-left: #808080 1px solid; border-bottom: #808080 1px solid; background-color: #ffffff"><img alt="" src="https://www.52php.cn/res/2019/02-14/22/a76e9bb6ed00cf1c9c9f4ee2f04b558b.gif"&gt;<span id="Codehighlighter1_375_3764_Open_Text"><span style="color: #000000">{<img alt="" src="/Images/OutliningIndicators/InBlock.gif" align="top">????????<span style="color: #0000ff">private<span style="color: #000000">?<span style="color: #0000ff">object<span style="color: #000000">?dataSource;<img alt="" src="/Images/OutliningIndicators/InBlock.gif" align="top">????????<span style="color: #0000ff">private<span style="color: #000000">?<span style="color: #0000ff">int<span style="color: #000000">?deep?<span style="color: #000000">=<span style="color: #000000">?<span style="color: #800080">0<span style="color: #000000">;?<img alt="" src="/Images/OutliningIndicators/InBlock.gif" align="top"><img id="Codehighlighter1_452_1120_Closed_Image" onclick="code_collapse_toggle(this);" alt="" src="/Images/OutliningIndicators/ContractedSubBlock.gif" align="top"><img id="Codehighlighter1_452_1120_Open_Image" style="display: none" onclick="code_collapse_toggle(this);" alt="" src="/Images/OutliningIndicators/ExpandedSubBlockStart.gif" align="top">????????<span id="Codehighlighter1_452_1120_Closed_Text" style="border-right: #808080 1px solid; border-top: #808080 1px solid; border-left: #808080 1px solid; border-bottom: #808080 1px solid; background-color: #ffffff">----重写----<span id="Codehighlighter1_452_1120_Open_Text" style="display: none"><span style="color: #0000ff">#region<span style="color: #000000">?----重写----<span style="color: #000000"><img alt="" src="/Images/OutliningIndicators/InBlock.gif" align="top">????????<span style="color: #0000ff">public<span style="color: #000000">?<span style="color: #0000ff">override<span style="color: #000000">?<span style="color: #0000ff">object<span style="color: #000000">?DataSource<img id="Codehighlighter1_521_701_Open_Image" onclick="code_collapse_toggle(this);" alt="" src="/Images/OutliningIndicators/ExpandedSubBlockStart.gif" align="top"><img id="Codehighlighter1_521_701_Closed_Image" style="display: none" onclick="code_collapse_toggle(this);" alt="" src="/Images/OutliningIndicators/ContractedSubBlock.gif" align="top">????????<span id="Codehighlighter1_521_701_Closed_Text" style="border-right: #808080 1px solid; border-top: #808080 1px solid; display: none; border-left: #808080 1px solid; border-bottom: #808080 1px solid; background-color: #ffffff"><img alt="" src="https://www.52php.cn/res/2019/02-14/22/a76e9bb6ed00cf1c9c9f4ee2f04b558b.gif"&gt;<span id="Codehighlighter1_521_701_Open_Text"><span style="color: #000000">{<img alt="" src="/Images/OutliningIndicators/InBlock.gif" align="top">????????????<span style="color: #0000ff">get<span style="color: #000000"><img id="Codehighlighter1_551_606_Open_Image" onclick="code_collapse_toggle(this);" alt="" src="/Images/OutliningIndicators/ExpandedSubBlockStart.gif" align="top"><img id="Codehighlighter1_551_606_Closed_Image" style="display: none" onclick="code_collapse_toggle(this);" alt="" src="/Images/OutliningIndicators/ContractedSubBlock.gif" align="top">????????????<span id="Codehighlighter1_551_606_Closed_Text" style="border-right: #808080 1px solid; border-top: #808080 1px solid; display: none; border-left: #808080 1px solid; border-bottom: #808080 1px solid; background-color: #ffffff"><img alt="" src="https://www.52php.cn/res/2019/02-14/22/a76e9bb6ed00cf1c9c9f4ee2f04b558b.gif"&gt;<span id="Codehighlighter1_551_606_Open_Text"><span style="color: #000000">{<img alt="" src="/Images/OutliningIndicators/InBlock.gif" align="top">????????????????<span style="color: #0000ff">return<span style="color: #000000">?<span style="color: #0000ff">this<span style="color: #000000">.dataSource;<img alt="" src="/Images/OutliningIndicators/ExpandedSubBlockEnd.gif" align="top">????????????}<span style="color: #000000"><img alt="" src="/Images/OutliningIndicators/InBlock.gif" align="top">????????????<span style="color: #0000ff">set<span style="color: #000000"><img id="Codehighlighter1_635_691_Open_Image" onclick="code_collapse_toggle(this);" alt="" src="/Images/OutliningIndicators/ExpandedSubBlockStart.gif" align="top"><img id="Codehighlighter1_635_691_Closed_Image" style="display: none" onclick="code_collapse_toggle(this);" alt="" src="/Images/OutliningIndicators/ContractedSubBlock.gif" align="top">????????????<span id="Codehighlighter1_635_691_Closed_Text" style="border-right: #808080 1px solid; border-top: #808080 1px solid; display: none; border-left: #808080 1px solid; border-bottom: #808080 1px solid; background-color: #ffffff"><img alt="" src="https://www.52php.cn/res/2019/02-14/22/a76e9bb6ed00cf1c9c9f4ee2f04b558b.gif"&gt;<span id="Codehighlighter1_635_691_Open_Text"><span style="color: #000000">{<img alt="" src="/Images/OutliningIndicators/InBlock.gif" align="top">????????????????<span style="color: #0000ff">this<span style="color: #000000">.dataSource?<span style="color: #000000">=<span style="color: #000000">?value;<img alt="" src="/Images/OutliningIndicators/ExpandedSubBlockEnd.gif" align="top">????????????}<span style="color: #000000"><img alt="" src="/Images/OutliningIndicators/ExpandedSubBlockEnd.gif" align="top">????????}<span style="color: #000000"><img alt="" src="/Images/OutliningIndicators/InBlock.gif" align="top">????????<span style="color: #0000ff">public<span style="color: #000000">?<span style="color: #0000ff">override<span style="color: #000000">?<span style="color: #0000ff">void<span style="color: #000000">?DataBind()<img id="Codehighlighter1_750_1101_Open_Image" onclick="code_collapse_toggle(this);" alt="" src="/Images/OutliningIndicators/ExpandedSubBlockStart.gif" align="top"><img id="Codehighlighter1_750_1101_Closed_Image" style="display: none" onclick="code_collapse_toggle(this);" alt="" src="/Images/OutliningIndicators/ContractedSubBlock.gif" align="top">????????<span id="Codehighlighter1_750_1101_Closed_Text" style="border-right: #808080 1px solid; border-top: #808080 1px solid; display: none; border-left: #808080 1px solid; border-bottom: #808080 1px solid; background-color: #ffffff"><img alt="" src="https://www.52php.cn/res/2019/02-14/22/a76e9bb6ed00cf1c9c9f4ee2f04b558b.gif"&gt;<span id="Codehighlighter1_750_1101_Open_Text"><span style="color: #000000">{<img alt="" src="/Images/OutliningIndicators/InBlock.gif" align="top">????????????<span style="color: #0000ff">if<span style="color: #000000">?(ChildProperty?<span style="color: #000000">==<span style="color: #000000">?<span style="color: #0000ff">null<span style="color: #000000">)<img id="Codehighlighter1_803_878_Open_Image" onclick="code_collapse_toggle(this);" alt="" src="/Images/OutliningIndicators/ExpandedSubBlockStart.gif" align="top"><img id="Codehighlighter1_803_878_Closed_Image" style="display: none" onclick="code_collapse_toggle(this);" alt="" src="/Images/OutliningIndicators/ContractedSubBlock.gif" align="top">????????????<span id="Codehighlighter1_803_878_Closed_Text" style="border-right: #808080 1px solid; border-top: #808080 1px solid; display: none; border-left: #808080 1px solid; border-bottom: #808080 1px solid; background-color: #ffffff"><img alt="" src="https://www.52php.cn/res/2019/02-14/22/a76e9bb6ed00cf1c9c9f4ee2f04b558b.gif"&gt;<span id="Codehighlighter1_803_878_Open_Text"><span style="color: #000000">{<img alt="" src="/Images/OutliningIndicators/InBlock.gif" align="top">????????????????<span style="color: #0000ff">throw<span style="color: #000000">?<span style="color: #0000ff">new<span style="color: #000000">?Exception(<span style="color: #800000">"<span style="color: #800000">ChildProperty参数必须设置<span style="color: #800000">"<span style="color: #000000">);<img alt="" src="/Images/OutliningIndicators/ExpandedSubBlockEnd.gif" align="top">????????????}<span style="color: #000000"><img alt="" src="/Images/OutliningIndicators/InBlock.gif" align="top">????????????<span style="color: #0000ff">this<span style="color: #000000">.Items.Clear();<img alt="" src="/Images/OutliningIndicators/InBlock.gif" align="top">????????????ListItemCollection?items<span style="color: #000000">=<span style="color: #000000">ConvertTreeToList(dataSource);<img alt="" src="/Images/OutliningIndicators/InBlock.gif" align="top">????????????<span style="color: #0000ff">foreach<span style="color: #000000">?(ListItem?item?<span style="color: #0000ff">in<span style="color: #000000">?items)<img id="Codehighlighter1_1036_1089_Open_Image" onclick="code_collapse_toggle(this);" alt="" src="/Images/OutliningIndicators/ExpandedSubBlockStart.gif" align="top"><img id="Codehighlighter1_1036_1089_Closed_Image" style="display: none" onclick="code_collapse_toggle(this);" alt="" src="/Images/OutliningIndicators/ContractedSubBlock.gif" align="top">????????????<span id="Codehighlighter1_1036_1089_Closed_Text" style="border-right: #808080 1px solid; border-top: #808080 1px solid; display: none; border-left: #808080 1px solid; border-bottom: #808080 1px solid; background-color: #ffffff"><img alt="" src="https://www.52php.cn/res/2019/02-14/22/a76e9bb6ed00cf1c9c9f4ee2f04b558b.gif"&gt;<span id="Codehighlighter1_1036_1089_Open_Text"><span style="color: #000000">{<img alt="" src="/Images/OutliningIndicators/InBlock.gif" align="top">????????????????<span style="color: #0000ff">this<span style="color: #000000">.Items.Add(item);<img alt="" src="/Images/OutliningIndicators/ExpandedSubBlockEnd.gif" align="top">????????????}<span style="color: #000000">?<img alt="" src="/Images/OutliningIndicators/InBlock.gif" align="top"><img alt="" src="/Images/OutliningIndicators/ExpandedSubBlockEnd.gif" align="top">????????}<span style="color: #000000"><img alt="" src="/Images/OutliningIndicators/ExpandedSubBlockEnd.gif" align="top">????????<span style="color: #0000ff">#endregion<span style="color: #000000">?<span style="color: #000000"><img alt="" src="/Images/OutliningIndicators/InBlock.gif" align="top"><img id="Codehighlighter1_1131_2931_Closed_Image" onclick="code_collapse_toggle(this);" alt="" src="/Images/OutliningIndicators/ContractedSubBlock.gif" align="top"><img id="Codehighlighter1_1131_2931_Open_Image" style="display: none" onclick="code_collapse_toggle(this);" alt="" src="/Images/OutliningIndicators/ExpandedSubBlockStart.gif" align="top">????????<span id="Codehighlighter1_1131_2931_Closed_Text" style="border-right: #808080 1px solid; border-top: #808080 1px solid; border-left: #808080 1px solid; border-bottom: #808080 1px solid; background-color: #ffffff">----私有方法----<span id="Codehighlighter1_1131_2931_Open_Text" style="display: none"><span style="color: #0000ff">#region<span style="color: #000000">?----私有方法----<span style="color: #000000"><img alt="" src="/Images/OutliningIndicators/InBlock.gif" align="top">????????<span style="color: #0000ff">private<span style="color: #000000">?ListItemCollection?ConvertTreeToList(<span style="color: #0000ff">object<span style="color: #000000">?root)<img id="Codehighlighter1_1226_1427_Open_Image" onclick="code_collapse_toggle(this);" alt="" src="/Images/OutliningIndicators/ExpandedSubBlockStart.gif" align="top"><img id="Codehighlighter1_1226_1427_Closed_Image" style="display: none" onclick="code_collapse_toggle(this);" alt="" src="/Images/OutliningIndicators/ContractedSubBlock.gif" align="top">????????<span id="Codehighlighter1_1226_1427_Closed_Text" style="border-right: #808080 1px solid; border-top: #808080 1px solid; display: none; border-left: #808080 1px solid; border-bottom: #808080 1px solid; background-color: #ffffff"><img alt="" src="https://www.52php.cn/res/2019/02-14/22/a76e9bb6ed00cf1c9c9f4ee2f04b558b.gif"&gt;<span id="Codehighlighter1_1226_1427_Open_Text"><span style="color: #000000">{<img alt="" src="/Images/OutliningIndicators/InBlock.gif" align="top">????????????deep?<span style="color: #000000">=<span style="color: #000000">?<span style="color: #800080">0<span style="color: #000000">;<img alt="" src="/Images/OutliningIndicators/InBlock.gif" align="top">????????????ListItemCollection?list?<span style="color: #000000">=<span style="color: #000000">??<span style="color: #0000ff">new<span style="color: #000000">?ListItemCollection();<img alt="" src="/Images/OutliningIndicators/InBlock.gif" align="top">????????????list.Add(GetListItem(root));<img alt="" src="/Images/OutliningIndicators/InBlock.gif" align="top">????????????ConvertTree(list,?root);<img alt="" src="/Images/OutliningIndicators/InBlock.gif" align="top">????????????<span style="color: #0000ff">return<span style="color: #000000">?list;<img alt="" src="/Images/OutliningIndicators/ExpandedSubBlockEnd.gif" align="top">????????}<span style="color: #000000"><img id="Codehighlighter1_1436_1572_Open_Image" onclick="code_collapse_toggle(this);" alt="" src="/Images/OutliningIndicators/ExpandedSubBlockStart.gif" align="top"><img id="Codehighlighter1_1436_1572_Closed_Image" style="display: none" onclick="code_collapse_toggle(this);" alt="" src="/Images/OutliningIndicators/ContractedSubBlock.gif" align="top">????????<span id="Codehighlighter1_1436_1572_Closed_Text" style="border-right: #808080 1px solid; border-top: #808080 1px solid; display: none; border-left: #808080 1px solid; border-bottom: #808080 1px solid; background-color: #ffffff">/**/<span id="Codehighlighter1_1436_1572_Open_Text"><span style="color: #808080">///<span style="color: #008000">?<span style="color: #808080">

具体调用示例：

1，将该控件添加到aspx页面中并设置必要的属性。

2，在页面的后台代码中添加数据源并进行数据绑定。

Code highlighting produced by Actipro CodeHighlighter (freeware)
http://www.CodeHighlighter.com/

-->

运行后的效果就是： 中国

由于本人接触服务器控件开发的时间并不长，对服务器控件开发经验还不足，该控件有需要改进或有错误的地方希望大家指正。

另外这个控件目前我发现的一个问题就是我将DataBind方法完全重写了，所以控件的DataTextFormatString失效了，由于很少使用这个属性，所以一般不影响使用。不知道有什么办法能够解决这个问题？

（编辑：李大同）

【声明】本站内容均来自网络，其相关言论仅代表作者个人观点，不代表本站立场。若无意侵犯到您的权利，请及时与联系站长删除相关内容!