function selectChange() { 
      if ($("select option").is(":selected")) { 
        $("#btn11").click(); 
      } 
    } 

 <asp:DropDownList ID="ddlNeedPage" runat="server" AutoPostBack="true" onchange="return selectChange();">
 </asp:DropDownList>

function clearData() { 
      //$("#<%=_gvGuest.ClientID %>").empty(); 
      $("#_gvGuest").empty(); 
      //$("#<%=lblMessage.ClientID %>").hide(); 
      $("#lblMessage").hide(); 
    } 

<asp:LinkButton ID="lnkFirstPage" runat="server" <span style="color:#ff0000;">OnClientClick="return clearData();"</span> 
CommandName="Page" CommandArgument="First" Enabled="<%# ((GridView)Container.Parent.Parent).PageIndex != 0 %>">第一页</asp:LinkButton> 

<asp:Button ID="btn11" runat="server" CssClass="btnPage"Style="display: none;" OnClick="btn11_Click" OnClientClick="return clearData2();"/>

function clearData2() { 
      var hidDDL = $("#_gvGuest_ddlNeedPage").val(); 
      $("#hidNeedPage").attr("value", hidDDL); 
      $("#_gvGuest").empty(); 
      $("#lblMessage").hide(); 
    } 

protected void btn11_Click(object sender, EventArgs e) 
    { 
 
      if (!string.IsNullOrEmpty(hidNeedPage.Value)) 
      { 
        _gvGuest.PageIndex = Convert.ToInt32(hidNeedPage.Value); 
        BindData(); 
      } 
    }