using System;

 using System.Collections.Generic;

 using System.Linq;

 using System.Web;

 using System.Web.UI.WebControls;

 namespace GetDateDome

 {

     public class ListBoxEx:ListBox

     {

         protected override object SaveViewState()

         {

             // create object array for Item count + 1

             object[] allStates = new object[this.Items.Count + ];

             // the +1 is to hold the base info

             object baseState = base.SaveViewState();

             allStates[] = baseState;

             Int32 i = ;

             // now loop through and save each Style attribute for the List

             foreach (ListItem li in this.Items)

             {

                 Int32 j = ;

                 string[][] attributes = new string[li.Attributes.Count][];

                 foreach (string attribute in li.Attributes.Keys)

                 {

                     attributes[j++] = new string[] { attribute, li.Attributes[attribute] };

                 }

                 allStates[i++] = attributes;

             }

             return allStates;

         }

         protected override void LoadViewState(object savedState)

         {

             if (savedState != null)

             {

                 object[] myState = (object[])savedState;

                 // restore base first

                 if (myState[] != null)

                     base.LoadViewState(myState[]);

                 Int32 i = ;

                 foreach (ListItem li in this.Items)

                 {

                     // loop through and restore each style attribute

                     foreach (string[] attribute in (string[][])myState[i++])

                     {

                         li.Attributes[attribute[]] = attribute[];

                     }

                 }

             }

         }

     }

 }

 <%@ Register assembly="GetDateDome" namespace="GetDateDome" tagprefix="my" %>

  <my:ListBoxEx ID="lstUnselectCol" runat="server" Style="width: 100%;height:100%;" ></my:ListBoxEx>

             //设置属性

             ListItem p = new ListItem(i["Item"].ToString(), i["value"].ToString());

             p.Attributes.Add("type", i["type"].ToString());

             lstUnselectCol.Items.Add(p);

             //获取属性

             string msg = srcList.SelectedItem.Attributes["type"];