I have the following view inside of my grid view.

<View>
<ext:GridView ID="GridView1" runat="server">
<GetRowClass Fn="getRowClass" />
</ext:GridView>
<ext:GroupingView
ID="GroupingView1"
HideGroupedColumn="true"
runat="server"
ForceFit="true"
GroupTextTpl='{text} ({[values.rs.length]} {[values.rs.length > 1 ? "Items" : "Item"]})'
EnableRowBody="true">
<GetRowClass Handler="var d = record.data; rowParams.body = String.format('<div style=\'padding:0 5px 5px 5px;\'>The {0} [{1}] requires light conditions of <i>{2}</i>.<br /><b>Price: {3}</b></div>', d.Common, d.Botanical, d.Light, Ext.util.Format.usMoney(d.Price));" />
</ext:GroupingView>
</View>

This creates the following error.

Only one item can be added to this Items Collection.