Panels with custom control content all loaded at once. Prevent children pages from loading?

[chearner]

I have a parent page with a TabPanel. To split up the code, I have each panel item within the TabPanel load a custom control. Most of these have a gridpanel.

How do I prevent each of these subpages from loading during the initial parent page load? One, all children pages loading at once would slow app down, and two, the gridpanels on subsequent tabs do not auto expand to fill the parent tabpanel width.

<ext:TabPanel ID="panelTabs" runat="server" AutoHeight="true" AutoWidth="true">
            <Items>
                <ext:Panel ID="panelGrid1" runat="server" Title="Grid 1">
                    <Content>
                        <uc:Panel1 ID="Panel1" runat="server" />
                    </Content>
                </ext:Panel>
                <ext:Panel ID="panelGrid2" runat="server" Title="Grid 2">
                    <Content>
                        <uc:Panel2 ID="Panel2" runat="server" />
                    </Content>
                </ext:Panel>
                 ...
            </Items>
        </ext:TabPanel>

[Vladimir]

1. Use AutoLoad Merge mode
https://examples1.ext.net/#/Panel/Basic/AutoLoad_MergeMode/

2. Wrap GridPanel in the user control by FitLayout control (please note that FitLayout must be single top level control)

[chearner]

When I try to use <ext:FitLayout runat="server">...my gridlayout...</ext:FitLayout>...

Type 'Ext.Net.FitLayout' does not have a public property named 'GridPanel'.

[Vladimir]

Use Items property of FitLayout

[chearner]

I found this to work, loading the .aspx page when I click on a tab. This 'parent' page loads the 'children' when a tab is clicked.

How can I pass that Parameter on the parent page (for each tab) into the children dynamically, I don't want to hard code it?

<ext:Parameter Name="domain" Mode="Value" Value=" --- want to put it here. Request['domain'] ---- " />

<ext:TabPanel ID="panelTabs" runat="server" Height="400">
<Items>
<ext:Panel ID="panelUsers" runat="server" Title="Users">
<AutoLoad Url="PanelUsers.aspx" Mode="IFrame" ReloadOnEvent="true" NoCache="true" Scripts="true" ShowMask="True">
   <Params>
      <ext:Parameter Name="domain" Mode="Value" Value="google.com" />
   </Params>
</AutoLoad>
</ext:Panel>
...