Coolite 

        <ext:Window ID="winDetalle" runat="server" Icon="Star" Width="600" Height="290" Modal="true" 
            Maximizable="true" Minimizable="false" Hidden="true" Layout="Fit" InitCenter="true" >
            <Content>
                <ext:TabPanel ID="tabEdit" runat="server" ActiveTabIndex="0" Border="false" AnimScroll="true" AutoScroll="true">
                    <Items>
                        <ext:Panel ID="tabDetalle" runat="server" Icon="StarGrey" BodyStyle="padding:5px;" AutoScroll="true" Layout="Fit">
                            <Content>
                                <ext:FormPanel runat="server" ID="frmDetalle" MonitorPoll="1500" MonitorResize="true" MonitorValid="true" BodyStyle="padding:5px;" AutoScroll="true">
                                <Defaults>
                                    <ext:Parameter Name="MsgTarget" Value="side" />
                                </Defaults>
                                <Items>
                                    <ext:TextField ID="txtID" runat="server" FieldLabel="ID" Width="100" ReadOnly="true" />

     <DirectMethod()> _
    Public Sub AddNew()
        Try
            txtID.Text = ""
            winDetalle.Show()
        Catch ex As Exception
            Logger.Error("AddNew." & GetType(Admin_Admin_Favorites).Name, ex)
        End Try
    End Sub

        <ext:Viewport runat="server">
            <Items>
                <ext:BorderLayout runat="server">
                    <Center AnimFloat="true">
                        <ext:GridPanel ID="grdDatos" runat="server" MonitorResize="true"
                            TrackMouseOver="true">
                            <TopBar>
                                <ext:Toolbar runat="server">
                                    <Items>
                                        <ext:Button ID="btnAgregar" runat="server" Text="Add" Icon="Add">
                                            <Listeners>
                                                <Click Handler="Ext.net.DirectMethods.AddNew();" />
                                            </Listeners>
                                        </ext:Button>