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27.3.2 StrawPoll控件构建器
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27.3.2 StrawPoll控件构建器
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<div style='float:left;width:49%'>·<a href='100165703.htm'>27.2.3 创建合成的定制控件</a></div><div style='float:right;width:49%'>·<a href='100165704.htm'>27.3 测验民意的投票控件</a></div><div style='float:left;width:49%'>·<a href='100165705.htm'>27.3.1 Candidate 控件</a></div><div style='float:right;width:49%'>·<a href='100165707.htm'>27.3.3 测试民意的投票类型</a></div><div style='float:left;width:49%'>·<a href='100165708.htm'>27.3.4 测试民意的投票控件</a></div><div style='float:right;width:49%'>·<a href='100165709.htm'>27.4 小结</a></div></div>
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<link href="css.css" rel="stylesheet" type="text/css" /><h3 style='margin-top:8.15pt;margin-right:0cm;FTEL:8.15pt;margin-left:
0cm'><span lang=EN-US>27.3.2 StrawPoll</span><span style='font-family:
黑体'>控件构建器</span><span lang=EN-US> </span></h3>
<p class=MsoNormal><span style='font-family:宋体'>接下来就讨论如何把每个选项的</span><span
lang=EN-US>ASP.NET</span><span style='font-family:宋体'>代码转化为</span><span
lang=EN-US>StarwPoll</span><span style='font-family:宋体'>控件的子控件。为此，需要使用</span><span
lang=EN-US>ControlBuilderAttribute</span><span style='font-family:宋体'>属性把控件构建器与</span><span
lang=EN-US>StrawPoll</span><span style='font-family:宋体'>类联系起来。还需要把</span><span
lang=EN-US>ParseChildren</span><span style='font-family:宋体'>属性设置为</span><span
lang=EN-US>false</span><span style='font-family:宋体'>，指定不应把该子控件分析为</span><span
lang=EN-US>StrawPoll</span><span style='font-family:宋体'>类的属性：</span></p>
<p class=2 style='margin-top:6.5pt;margin-right:0cm;FTEL:0cm;
margin-left:21.45pt;FTEL:.0001pt;FTEL:18.45pt'><span
lang=EN-US> [
ControlBuilderAttribute(typeof(StrawPollControlBuilder)) ]</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt'><span lang=EN-US>
[ ParseChildren(false) ]</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt'><span lang=EN-US>
public class StrawPoll : System.Web.UI.WebControls.WebControl,</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt'><span lang=EN-US>
INamingContainer</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt'><span lang=EN-US>
{</span></p>
<p class=2 style='margin-top:0cm;margin-right:0cm;FTEL:6.5pt;
margin-left:21.45pt;FTEL:18.45pt'><span lang=EN-US> }</span></p>
<p class=MsoNormal><span style='font-family:宋体'>这里使用一个名称为</span><span
lang=EN-US>StarwPollControlBuilder</span><span style='font-family:宋体'>的类，这个类在</span><span
lang=EN-US>StrawPollControlBuilder.cs</span><span style='font-family:宋体'>中定义，如下所示：</span></p>
<p class=2 style='margin-top:6.5pt;margin-right:0cm;FTEL:0cm;
margin-left:21.45pt;FTEL:.0001pt;FTEL:18.45pt'><span
lang=EN-US> internal class StrawPollControlBuilder : ControlBuilder</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.0pt'><span
lang=EN-US> {</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.0pt'><span
lang=EN-US> public override Type
GetChildControlType(string tagName,</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.0pt'><span
lang=EN-US>
IDictionary attribs)</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.0pt'><span
lang=EN-US> {</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.0pt'><span
lang=EN-US> if (tagName.ToLower().EndsWith("candidate"))</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.0pt'><span
lang=EN-US>
return typeof(Candidate);</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.0pt'><span
lang=EN-US> return null;</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.0pt'><span
lang=EN-US> }</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.0pt'><span
lang=EN-US> </span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.0pt'><span
lang=EN-US> public override void
AppendLiteralString(string s)</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.0pt'><span
lang=EN-US> {</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.0pt'><span
lang=EN-US> // Do nothing, to
avoid embedded text being added to control</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.0pt'><span
lang=EN-US> }</span></p>
<p class=2 style='margin-top:0cm;margin-right:0cm;FTEL:6.5pt;
margin-left:21.45pt;FTEL:18.45pt'><span lang=EN-US> }</span></p>
<p class=MsoNormal><span style='font-family:宋体'>本例重写基类</span><span lang=EN-US>ControlBuilder</span><span
style='font-family:宋体'>的</span><span lang=EN-US>GetChildControlType()</span><span
style='font-family:宋体'>方法，返回</span><span lang=EN-US>Candidate</span><span
style='font-family:宋体'>类的类型，响应名称为</span><span lang=EN-US><Candidate></span><span
style='font-family:宋体'>的标记。事实上，为了确保在尽可能多的情况下都能顺利工作，我们要寻找以字符串</span><span
lang=EN-US>“Candidate”</span><span style='font-family:宋体'>结尾的标记名，这里不考虑</span><span
lang=EN-US>Candidate</span><span style='font-family:宋体'>的大小写。</span></p>
<p class=MsoNormal><span style='font-family:宋体'>此外，也重写</span><span lang=EN-US>AppendLiteralString()</span><span
style='font-family:宋体'>方法，忽略所有插入的文本，包括空白格，进而确保不会出现问题。</span></p>
<p class=MsoNormal><span style='font-family:宋体'>设置好之后，假定在</span><span
lang=EN-US>StrawPoll</span><span style='font-family:宋体'>中不包含其他的控件，则</span><span
lang=EN-US>StrawPoll</span><span style='font-family:宋体'>的</span><span
lang=EN-US>Contrlos</span><span style='font-family:宋体'>集合中包含所有的</span><span
lang=EN-US>Candidate</span><span style='font-family:宋体'>控件，而不会包含其他的控件。</span></p>
<p class=MsoNormal><span style='font-family:宋体'>注意，控件构建器利用了属性的集合。为了对此进行支持，需要给命名空间添加如下</span><span
lang=EN-US>using</span><span style='font-family:宋体'>语句：</span></p>
<p class=a6 style='margin-top:8.15pt;margin-right:0cm;FTEL:8.15pt;
margin-left:21.45pt;FTEL:18.45pt;background:#F2F2F2'><span lang=EN-US>
using System.Collections;</span></p>
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<h1 id="divCurrentNode2" style="color: #b83507; width: 100%; text-align: left; font-size: 12px; padding-left: 2px">当前章节:<a href='100165706.htm'><font color='red'>27.3.2 StrawPoll控件构建器</font></a></h1>
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<div style='float:left;width:49%'>·<a href='100165703.htm'>27.2.3 创建合成的定制控件</a></div><div style='float:right;width:49%'>·<a href='100165704.htm'>27.3 测验民意的投票控件</a></div><div style='float:left;width:49%'>·<a href='100165705.htm'>27.3.1 Candidate 控件</a></div><div style='float:right;width:49%'>·<a href='100165707.htm'>27.3.3 测试民意的投票类型</a></div><div style='float:left;width:49%'>·<a href='100165708.htm'>27.3.4 测试民意的投票控件</a></div><div style='float:right;width:49%'>·<a href='100165709.htm'>27.4 小结</a></div></div>
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