Here, i've problem with rowselectionmodel,i.e,Initially i bind data to grid ,then I select one record,and when i click GetData button,again I bind data(may contain old records) to store.Here My problem is when i click a record(which is already selected by user),that row not able to selected.how can i resolve this problem.

<ext:ResourceManager ID="rsmngr" runat="server" Theme="Neptune" />         
            <ext:Viewport ID="vwprtMyworks" runat="server" Layout="BorderLayout">
                    <ext:Panel ID="pnlMyWorks" runat="server" Region="Center" Layout="FormLayout" AutoScroll="true">
                            <ext:Button ID="btnGetData" runat="server" Text="GetData">
                                    <Click OnEvent="btnGetData_Click">
                                        <EventMask ShowMask="true" />


                            <ext:GridPanel ID="grdpnlMyWorks" runat="server" Layout="FormLayout"  Width="500">
                                    <ext:Store ID="strMyWorks" runat="server" PageSize="10" AutoDataBind="true">
                                            <ext:Model ID="mdlMyWorks" runat="server" IDProperty="TestOrderId">
                                                    <ext:ModelField Name="TestOrderId" />
                                                    <ext:ModelField Name="JobPackCode" />
                                                    <ext:ModelField Name="TestName" />
                                                    <ext:ModelField Name="TestOrderDescription" />
                                        <ext:Column ID="colJobPackCode" runat="server" Text="Code" DataIndex="JobPackCode" Width="100" />
                                        <ext:Column ID="colTestName" runat="server" Text="Test Name" DataIndex="TestName" Width="150" />
                                        <ext:Column ID="colTestNameOrderDescription" runat="server" DataIndex="TestOrderDescription" Text="Description" Flex="1" />                                 
                                    <ext:RowSelectionModel ID="rwselmdlMyWorks" Mode="Multi" runat="server">
public partial class WebForm2 : System.Web.UI.Page
        protected void Page_Load(object sender, EventArgs e)
            if (!IsPostBack)
 public class TestOrder
        public Guid TestOrderId { get; set; }
        public string TestName { get; set; }
        public string TestOrderDescription { get; set; }
        public string JobPackCode { get; set; }

        protected void btnGetData_Click(object sender, DirectEventArgs e)

        private void BindData()
            TestOrder to1 = new TestOrder();
            to1.TestOrderId = new Guid("276C19AA-41A4-4535-9447-00E7A0B6D5B9");
            to1.TestName = "Alkalinity Analysis";
            to1.JobPackCode = "00015/ML/15";
            to1.TestOrderDescription = "00015/ML/15 Alkalinity Analysis";

            TestOrder to2 = new TestOrder();
            to2.TestOrderId = new Guid("3FDC67DB-9E87-4D22-A0B2-077850669A42");
            to2.TestName = "PH";
            to2.JobPackCode = "00016/ML/15";
            to2.TestOrderDescription = "00016/ML/15 PH";

            List<TestOrder> lstTestOrder = new List<TestOrder>();
            strMyWorks.DataSource = lstTestOrder;