Asp 2.0 provide listbox control but one cannot seach in web application But the same is poosible in ajax 
How To use:
In the Source code window type:
 
<form id="form1" runat="server">
    <asp:ToolkitScriptManager ID="ToolkitScriptManager1" runat="server">
    </asp:ToolkitScriptManager>
    
Click on me to search an item    
    <asp:ListBox ID="ListBox1" runat="server">
        <asp:ListItem>India</asp:ListItem>
        <asp:ListItem>Pakistan</asp:ListItem>
        <asp:ListItem>Afganistan</asp:ListItem>
        <asp:ListItem>america</asp:ListItem>
          <asp:ListItem>south Africa</asp:ListItem>
            <asp:ListItem>London</asp:ListItem>
              <asp:ListItem>USA</asp:ListItem>
                <asp:ListItem>China</asp:ListItem>
                  <asp:ListItem>Canada</asp:ListItem>
                    <asp:ListItem>Washington</asp:ListItem>
    </asp:ListBox>
    <asp:ListSearchExtender ID="ListBox1_ListSearchExtender" runat="server" 
        Enabled="True"  PromptPosition="Top"  PromptText="Click on Listbox to search"  
        TargetControlID="ListBox1">
    </asp:ListSearchExtender>
    
       </form>
Here is the Code and its works .
what u need is just take a asp listbox control
Add an listbox extender with it u can specify the promptef text for the listbox searching 
Note:The Code also work for dropDown Searching