asp:DeclarativeCatalogPart WebPartsTemplate must have odd number of elements

I discovered an interesting anomaly today, working with ASP.NET and Web Parts, I had an issue whereby creating a CatalogZone caused the HTML generated from template to lose a whole lot of closing tags. This threw the whole page out the window as the CSS was stuffed. I did a LOT of Googling to no avail.

Finally I went into the tried and true method of trial and error; removing one element at a time until I found the problem bit. This was also anomalous as I have three pages with essentially the same code and only one breaks! I won’t bore you by going through every iteration and step I took, I’ll just bounce to the solution.

In their wisdom Microsoft has apparently made the template work for an odd number of elements, but an even number has a tantrum and is not composed correctly. It was only when I realised that that during my trial and error, the two working pages had 15 and 5 elements respectively, and the “broken” page had 6 elements; thinking this could not possibly be the issue, I checked and was astounded. The general response from my colleagues was “you’ve got to be f@$#en kidding me”. I swear, I’m not.

In summary, from an HTML point of view, this works:

<asp:CatalogZone ID="CatalogZone" runat="server">
	<ZoneTemplate>
		<asp:DeclarativeCatalogPart ID="DeclarativeCatalogPart" runat="server">
			<WebPartsTemplate>
				<tfr:stuff1 ID="stuff1" runat="server" />
				<tfr:stuff2 ID="stuff2" runat="server" />
				<tfr:stuff3 ID="stuff3" runat="server" />
			</WebPartsTemplate>
		</asp:DeclarativeCatalogPart>
		<asp:PageCatalogPart ID="PageCatalogPart" runat="server" />
	</ZoneTemplate>
</asp:CatalogZone>

and this doesn’t:

<asp:CatalogZone ID="CatalogZone" runat="server">
	<ZoneTemplate>
		<asp:DeclarativeCatalogPart ID="DeclarativeCatalogPart" runat="server">
			<WebPartsTemplate>
				<tfr:stuff1 ID="stuff1" runat="server" />
				<tfr:stuff2 ID="stuff2" runat="server" />
			</WebPartsTemplate>
		</asp:DeclarativeCatalogPart>
		<asp:PageCatalogPart ID="PageCatalogPart" runat="server" />
	</ZoneTemplate>
</asp:CatalogZone>