WPF refuses to Show design when using contextMenu

When i use ContextMenu in a window, then SharpDevelop IDE refuses to show design time of xaml file.

<Window.ContextMenu>
    <ContextMenu>
            <MenuItem Header="Add"/>
            <MenuItem Header="Change"/>
            <MenuItem Header="Find"/>
        </ContextMenu>
</Window.ContextMenu>

This is a WPF app using .NET framework 4.0.

PS: Same issue is as with nitly build and in stable release