C# - Itemplate Properties Not Available As Attributes?

I've added an ITemplate to Telerik's RadGrid control called SearchMenuTemplate ala:

[code]...

And the Template class looks something like (mandatory override methods like createchildcontrol have been omitted for brevity):

[ParseChildren(true)]
class searchBar : CompositeControl, INamingContainer
{
public string rbStartsWithText { get; set; }
}

Now, in the source control window the RadGrid control sees the Template. But rbStartsWithText isn't an attribute on the node.

I want to see something like this (note: abs prefix is registered in the markup):

<abs:AbsRadGrid ID="rg" runat="server">
<SearchMenuTemplate rbStartsWithText="Starts With" />
</abs:AbsRadGrid>

Instead rbStartsWithText is throwing a green squiggly and telling me it's not a valid attribute of SearchMenuTemplate.