扩展DropDownList控件和ListBox控件 - 支持分组功能(optgroup标签)

using System;
using System.Collections.Generic;
using System.Text;
using System.ComponentModel;
using System.Web.UI;
namespace YYControls
{
/**//// <summary>
/// SmartDropDownList类的属性部分
/// </summary>
    public partial class SmartDropDownList
{
/**//// <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;
}
}
}
}

using System;
using System.Collections.Generic;
using System.Text;
using System.Data;
using System.Web.UI.WebControls;
using System.Web.UI;
using System.Web;
namespace YYControls
{
/**//// <summary>
/// SmartDropDownList类的属性部分
/// </summary>
    public partial class SmartDropDownList
{
/**//// <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();
}
}
}