ASP .NET 可编辑输入自动匹配的下拉框

<%@ Register TagPrefix="telerik" Namespace="Telerik.Web.UI" Assembly="Telerik.Web.UI" %>
　　　　<%@ Register TagPrefix="qsf" Namespace="Telerik.QuickStart" %>

 <telerik:RadComboBox RenderMode="Lightweight" ID="DropDownList1" AllowCustomText="true" AutoPostBack="True" runat="server" Width="110px" Height="400px"
  EmptyMessage="请输入小区名称" OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged" OnItemsRequested="DropDownList1_ItemsRequested" MarkFirstMatch="true" EnableLoadOnDemand="true"
   HighlightTemplatedItems="true" DropDownCssClass="exampleRadComboBox">
    </telerik:RadComboBox>

this.DropDownList1.DataSource = (new BLL_TArea()).GetAllAreaInfo();
   this.DropDownList1.DataTextField = "AREANAME";
   this.DropDownList1.DataValueField = "AREAGUID";
   this.DropDownList1.DataBind();
   DropDownList1.Items.FindItemByValue(BaseClass.Utility.Cookie.GetCookie("AreaGuid")).Selected = true;