Hi there,
I think that I've encountered a bug, setting up a UserControl with the XAML illustrated below, throws an exception in the VS2010 Designer.
If I delete the RadPanelBar from the XAML, the designer works again...
<UserControl x:Class="nVision.Office.Views.MainFrame"
mc:Ignorable="d"
Background="Transparent">
<Grid x:Name="LayoutRoot" Background="Transparent">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="Auto"/>
</Grid.ColumnDefinitions>
<telerik:RadOutlookBar Grid.Column="0" Name="radOutlookBar1" Width="250" MaxWidth="400" Margin="4,4,0,4" SelectionChanged="radOutlookBar1_SelectionChanged">
<telerik:RadOutlookBarItem Header="Home" Tag="/Views/Dashboard.xaml" />
<telerik:RadOutlookBarItem Header="Orders" Tag="/Views/Dashboard.xaml" />
<telerik:RadOutlookBarItem Header="Customers" Tag="/Views/Dashboard.xaml" />
<telerik:RadOutlookBarItem Header="Products" Tag="/Views/Dashboard.xaml" />
<telerik:RadOutlookBarItem Header="Reports" Tag="/Core/Modules/Test/TGridDScroll.xaml" />
<telerik:RadOutlookBarItem Header="Settings" Tag="/Core/Modules/Test/TGridPaging.xaml" />
<telerik:RadOutlookBarItem Header="Test" Tag="/Core/Modules/Test/Home.xaml"></telerik:RadOutlookBarItem>
</telerik:RadOutlookBar>
<sdk:Frame Grid.Column="1" Name="ContentFrame" Source="/Views/Dashboard.xaml" BorderThickness="0" Padding="0,2,0,0" JournalOwnership="OwnsJournal" />
<telerik:RadPanelBar Grid.Column="2" HorizontalAlignment="Left" Name="radPanelBar1" Width="150">
<telerik:RadPanelBarItem Name="Item1" DropPosition="Inside" Header="Item 1" TabNavigation="Once" />
<telerik:RadPanelBarItem Name="Item2" DropPosition="Inside" Header="Item 2" TabNavigation="Once" />
<telerik:RadPanelBarItem Name="Item3" DropPosition="Inside" Header="Item 3" TabNavigation="Once" />
<telerik:RadPanelBarItem Name="Item4" DropPosition="Inside" Header="Item 4" TabNavigation="Once" />
<telerik:RadPanelBarItem Name="Item5" DropPosition="Inside" Header="Item 5" TabNavigation="Once" />
<telerik:RadPanelBarItem Name="Item6" DropPosition="Inside" Header="Item 6" TabNavigation="Once" />
<telerik:RadPanelBarItem Name="Item7" DropPosition="Inside" Header="Item 7" TabNavigation="Once" />
<telerik:RadPanelBarItem Name="Item8" DropPosition="Inside" Header="Item 8" TabNavigation="Once" />
</telerik:RadPanelBar>
</Grid>
</UserControl>