DropDownList--有关于OptionGroup，Sort的话题

最近在项目中，要实现对DropDownList中的Option进行分组的功能。大家都知道传统的DropDownList是无法实现，以及对DropDownList的排序问题。所以么法子啊，  I make my own.
效果图:
  

代码如下：

<%@ Register Assembly="DropDownList" Namespace="WebDropDownList" TagPrefix="optGroup" %>
.
<form id="form1" runat="server">
        <div>
              <optGroup:DDL id="cboTest" runat="server"></optGroup:DDL>
        </div>
    </form>
.

NewDropDownList UI类:

 public partial class NewDropDownList : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            //设置OptionGroup1
            ListItem optGroup1 = new ListItem();
            optGroup1.Attributes.Add("optgroup", "OptionGroup1");
            //设置OptionGroup Id
            optGroup1.Attributes.Add("id", "1");
            this.cboTest.Items.Add(optGroup1);

            ListItem option1 = new ListItem("Visa", "4");
            this.cboTest.Items.Add(option1);

            ListItem option2 = new ListItem("Master", "3");
            this.cboTest.Items.Add(option2);

            ListItem option3 = new ListItem("Diners", "2");
            this.cboTest.Items.Add(option3);

            ListItem optGroup2 = new ListItem();
            optGroup2.Attributes.Add("optgroup", "OptionGroup2");
            optGroup2.Attributes.Add("id", "2");
            this.cboTest.Items.Add(optGroup2);

            ListItem option4 = new ListItem("Bank", "7");
            this.cboTest.Items.Add(option4);

            ListItem option5 = new ListItem("China", "5");
            this.cboTest.Items.Add(option5);

            //设置排序(true顺序，false则相反)
            //排序可以按ListItemText,或者按ListItemValue
            new DDL().SortListItem(this.cboTest, String.Empty, true);
        }
    }

  1DDL 控件类:
  2
  3public class DDL : DropDownList
  4    {
  5        private const String OPTIONGROUP = "optgroup";
  6        private const String OPTIONID = "id";
  7        private const String OPTION = "option";
  8        private const String LABEL = "label";
  9        private const String VALUE = "value";
 10        private const String SELECTED = "selected";
 11
 12        //over write RenderContents
 13        protected override void RenderContents(HtmlTextWriter writer)
 14        {
 15            String optgroup = String.Empty;
 16            String id = String.Empty;
 17
 18            ArrayList optOptionGroups = new ArrayList();
 19
 20            foreach (ListItem item in this.Items)
 21            {
 22                if (item.Attributes[OPTIONGROUP] == null)
 23                {
 24                    RenderListItem(item, writer);
 25                }
 26                else
 27                {
 28                    optgroup = item.Attributes[OPTIONGROUP];
 29                    id = item.Attributes[OPTIONID];
 30
 31                    if (optOptionGroups.Contains(optgroup))
 32                    {
 33                        RenderListItem(item, writer);
 34                    }
 35                    else
 36                    {
 37                        if (optOptionGroups.Count > 0)
 38                        {
 39                            optgroupEndTag(writer);
 40                        }
 41                        optgroupBeginTag(id, optgroup, writer);
 42                        optOptionGroups.Add(optgroup);
 43                    }
 44                }
 45            }
 46
 47            if (optOptionGroups.Count > 0)
 48            {
 49                optgroupEndTag(writer);
 50            }
 51        }
 52
 53
 54        /**//// <summary>
 55        /// Render List Item
 56        /// </summary>
 57        /// <param name="item"></param>
 58        /// <param name="writer"></param>
 59        private void RenderListItem(ListItem item, HtmlTextWriter writer)
 60        {
 61            writer.WriteBeginTag(OPTION);
 62            writer.WriteAttribute(VALUE, item.Value, true);
 63
 64            if (item.Selected)
 65            {
 66                writer.WriteAttribute(SELECTED, SELECTED, false);
 67            }
 68
 69            foreach (String key in item.Attributes.Keys)
 70            {
 71                writer.WriteAttribute(key, item.Attributes[key]);
 72            }
 73
 74            writer.Write(HtmlTextWriter.TagRightChar);
 75            HttpUtility.HtmlEncode(item.Text, writer);
 76            writer.WriteEndTag(OPTION);
 77            writer.WriteLine();
 78        }
 79
 80        //选项添加到组中
 81        private void optgroupBeginTag(String id, String name, HtmlTextWriter writer)
 82        {
 83            writer.WriteBeginTag(OPTIONGROUP);
 84            writer.WriteAttribute(LABEL, name);
 85            writer.WriteAttribute(OPTIONID, id);
 86            writer.Write(HtmlTextWriter.TagRightChar);
 87            writer.WriteLine();
 88        }
 89
 90        private void optgroupEndTag(HtmlTextWriter writer)
 91        {
 92            writer.WriteEndTag(OPTIONGROUP);
 93            writer.WriteLine();
 94        }
 95
 96        /**//// <summary>
 97        /// 对ListItem进行排序[顺序排序]
 98        /// </summary>
 99        /// <param name="sortBy"></param>
100        /// <param name="dropDownList"></param>
101        public void SortListItem(DropDownList dropDownList, String sortBy, Boolean sortType)
102        {
103            ListItem[] listItem = new ListItem[dropDownList.Items.Count];
104
105            dropDownList.Items.CopyTo(listItem, 0);
106
107            if (!sortBy.Equals(String.Empty))
108            {
109                Array.Sort(listItem, new ListItemTextComparer());
110            }
111            else
112            {
113                Array.Sort(listItem, new ListItemValueComparer());
114
115            }
116            if (!sortType)
117            {
118                Array.Reverse(listItem);
119            }
120
121            dropDownList.Items.Clear();
122            dropDownList.Items.AddRange(listItem);
123        }
124
125        /**//// <summary>
126        /// 按ListItem的Text或者Value进行排序
127        /// </summary>
128        internal class ListItemTextComparer : IComparer
129        {
130            public int Compare(object x, object y)
131            {
132                return new CaseInsensitiveComparer().Compare((x as ListItem).Text, (y as ListItem).Text);
133            }
134        }
135
136        /**//// <summary>
137        /// 按ListItem的Value进行排序
138        /// </summary>
139        internal class ListItemValueComparer : IComparer
140        {
141            public int Compare(object x, object y)
142            {
143                return new CaseInsensitiveComparer().Compare((x as ListItem).Value, (y as ListItem).Value);
144            }
145        }
146    }