UserControl does not have public property named ContentTemplate
===

This question has been asked a few dozen times before; but has never been solved.

i have an **`UpdatePanel`**

    <asp:UpdatePanel ID="UpdatePanelSetupToolbar" runat="server">
       <ContentTemplate>
          ...			
       </ContentTemplate>
    </asp:UpdatePanel>		

But the *visual page designer* in  Visual Studio (2010 (Professional (Windows (7 (Professional (64-bit)))))) gives the error:

> **Error Creating Control** - UpdatePanelSetupToolbar
>
> Type 'System.Web.UI.UserControl' does not have a public property named 'ContentTemplate'.

![enter image description here][1]  
<sup><sup>*Edit: pretty colors in pretty screenshots are added for pretty effect*</sup></sup>

Now, strictly speaking, that is true: [`UserControl`](http://msdn.microsoft.com/en-us/library/system.web.ui.usercontrol_properties) does **not** have a public property called `ContentTemplate`.

Fortunately my `UpdatePanel` is an **`UpdatePanel`**, and it **does** have a public property named [`'ContentTemplate'`](http://msdn.microsoft.com/en-us/library/system.web.ui.updatepanel.contenttemplate.aspx).

So how do i convince Visual Studio that my `UpdatePanel` is an `UpdatePanel`?

Important additional notes
------------

The code above doesn't actually fail as is:


    <asp:UpdatePanel ID="UpdatePanelSetupToolbar" runat="server">
       <ContentTemplate>
          ...			
       </ContentTemplate>
    </asp:UpdatePanel>	

It only fails when i have content inside the `...` ContentTemplate:

		<asp:UpdatePanel ID="UpdatePanelSetupToolbar" runat="server">
			<ContentTemplate>
				<Vista:Toolbar ID="ToolbarSetup" runat="server">
					<ContentTemplate>
						<asp:LinkButton ID="bbSetupDays" ToolTip="Specify how many allocations will be available on these selected days"
						OnClick="bbSetupDays_Click"                                        
						runat="server">Setup Selected Days</asp:LinkButton>			
					</ContentTemplate>
				</Vista:Toolbar>		
			</ContentTemplate>
		</asp:UpdatePanel>		

- but Visual Studio is not complaining about inner `ToolbarSetup`
- it's complaining about the outer `UpdatePanelSetupToolbar` control

So what's the deal with 

> Type '%s' does not have a public property named '%s'.

?

Unimportant additional notes
-------

The ASP.net web-site compiles, builds, and runs *fine*. It's just the Visual Studio (2010) designer that complains.


So what's the deal with `Type '%s' does not have a public property named '%s'.`?


  [1]: http://i.stack.imgur.com/JAFPt.png