Hi, I have a form panel and when I add controls dynamically to it I get following JavaScript error.

Uncaught TypeError: Cannot read property 'removeCls' of null
at ctor.toggleInvalidCls (ext.axd?v=4.7.1:20)
at ctor.renderActiveError (ext.axd?v=4.7.1:20)
at ctor.renderActiveError (ext.axd?v=4.7.1:20)
at ctor.onRender (ext.axd?v=4.7.1:20)
at ctor.callParent (ext.axd?v=4.7.1:20)
at ctor.onRender (ext.axd?v=4.7.1:581)
at ctor.callParent (ext.axd?v=4.7.1:20)
at ctor.onRender (ext.axd?v=4.7.1:656)
at ctor.onRender (ext.axd?v=4.7.1:20)
at ctor.finishRender (ext.axd?v=4.7.1:20)


My Code
.ascx File

<ext:FormPanel
ID="frmPanelGeneral"
runat="server"
BodyPaddingSummary="5 5 0"
Width="650"
Frame="true"
AutoScroll="true"
ButtonAlign="Center">
<FieldDefaults LabelWidth="135" InputWidth="325">
</FieldDefaults>

<Items>
</Items>
<Buttons>
<ext:Button runat="server" Text="Save">
<DirectEvents>
<Click OnEvent="SavePolicyInfo"></Click>
</DirectEvents>
</ext:Button>
<ext:Button runat="server" ID="Button1" Text="Cancel">
<Listeners>
<Click Handler="fnUploadWindowClose();" />
</Listeners>
</ext:Button>
</Buttons>
</ext:FormPanel>


.ascx.cs file:


textField = new Ext.Net.TextField();
textField.ID = "txt" + key;
textField.FieldLabel = key;
textField.Name = key;
frmPanelGeneral.Items.Add(textField);
textField.Render();