using System;
2 using System.Collections.Generic;
3 using System.Linq;
4 using System.Text;
5 using System.Web.UI.WebControls;
6 using System.Web.UI;
7 using System.ComponentModel;
8 using System.Web;
9
namespace mydream.Controls
{
[ToolboxData("<{0}:SmartDropDownList runat=server></{0}:SmartDropDownList>")]
public class SmartDropDownList : DropDownList
{
/// <summary>
/// 构造函数
/// </summary>
public SmartDropDownList() { }
/// <summary>
/// 将控件的内容呈现到指定的编写器中
/// </summary>
/// <param name="writer"></param>
protected override void RenderContents(HtmlTextWriter writer)
{
OptionGroupRenderContents(writer);
}
/// <summary>
/// 呈现Option或OptionGroup
/// </summary>
/// <param name="writer">writer</param>
private void OptionGroupRenderContents(HtmlTextWriter writer)
{
// 是否需要呈现OptionGroup的EndTag
bool writerEndTag = false;
foreach (ListItem li in this.Items)
{
// 如果没有optgroup属性则呈现Option
if (li.Value != this.OptionGroupValue)
{
// 呈现Option
RenderListItem(li, writer);
}
// 如果有optgroup属性则呈现OptionGroup
else
{
if (writerEndTag)
// 呈现OptionGroup的EndTag
OptionGroupEndTag(writer);
else
writerEndTag = true;
// 呈现OptionGroup的BeginTag
OptionGroupBeginTag(li, writer);
}
}
if (writerEndTag)
// 呈现OptionGroup的EndTag
OptionGroupEndTag(writer);
}
/// <summary>
/// 呈现OptionGroup的BeginTag
/// </summary>
/// <param name="li">OptionGroup数据项</param>
/// <param name="writer">writer</param>
private void OptionGroupBeginTag(ListItem li, HtmlTextWriter writer)
{
writer.WriteBeginTag("optgroup");
// 写入OptionGroup的label
writer.WriteAttribute("label", li.Text);
foreach (string key in li.Attributes.Keys)
{
// 写入OptionGroup的其它属性
writer.WriteAttribute(key, li.Attributes[key]);
}
writer.Write(HtmlTextWriter.TagRightChar);
writer.WriteLine();
}
/// <summary>
/// 呈现OptionGroup的EndTag
/// </summary>
/// <param name="writer">writer</param>
private void OptionGroupEndTag(HtmlTextWriter writer)
{
writer.WriteEndTag("optgroup");
writer.WriteLine();
}
/// <summary>
/// 呈现Option
/// </summary>
/// <param name="li">Option数据项</param>
/// <param name="writer">writer</param>
private void RenderListItem(ListItem li, HtmlTextWriter writer)
{
writer.WriteBeginTag("option");
// 写入Option的Value
writer.WriteAttribute("value", li.Value, true);
if (li.Selected)
{
// 如果该Option被选中则写入selected
writer.WriteAttribute("selected", "selected", false);
}
foreach (string key in li.Attributes.Keys)
{
// 写入Option的其它属性
writer.WriteAttribute(key, li.Attributes[key]);
}
writer.Write(HtmlTextWriter.TagRightChar);
// 写入Option的Text
HttpUtility.HtmlEncode(li.Text, writer);
writer.WriteEndTag("option");
writer.WriteLine();
}
/// <summary>
/// 用于添加SmartDropDownList的分组项的ListItem的Value值
/// </summary>
[
Browsable(true),
Description("用于添加DropDownList的分组项的ListItem的Value值"),
Category("扩展")
]
public virtual string OptionGroupValue
{
get
{
string s = (string)ViewState["OptionGroupValue"];
return (s == null) ? "optgroup" : s;
}
set
{
ViewState["OptionGroupValue"] = value;
}
}
}
}
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="smartDropDownList.aspx.cs" Inherits="smartDropDownList" %>
<%@ Register Assembly="Controls" Namespace="mydream.Controls" TagPrefix="cc1" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
</head>
<body>
<form id="form1" runat="server">
<div>
<cc1:SmartDropDownList ID="SmartDropDownList1" runat="server">
</cc1:SmartDropDownList>
</div>
</form>
</body>
</html>
