用Ajax插件

<asp:TextBox ID="txtWeb" runat="server" Width="195px"></asp:TextBox><cc1:AutoCompleteExtender ID="AutoCompleteExtender1" runat="server" ServicePath="~/WebService.asmx"
                    ServiceMethod="GetHot" EnableCaching="true" MinimumPrefixLength="1" CompletionSetCount="10"
                    TargetControlID="txtWeb">
                </cc1:AutoCompleteExtender>

---------------方法

  public static string[] GetHot(string keyword, int count)
    {   

        IList<string> results = new List<string>(count);
        string sql = "select top 10 * from Email_Msg where websiteid like '%" + keyword + "%' order by id";
        IList<Email_Msg> list = GetSearchKeywordBySql(sql);
        foreach (Email_Msg item in list)
        {
            results.Add(item.Websiteid);
        }
        return results.ToArray();
    }

写出来的效果，不够理想，想更进一步的实现谷歌的功能，如果输入多个字符，可以更进一步的实现效果。达到精确。