Create a class for the view of the multi-view widget designer 
The backbone of the view is a custom widget. The custom widget can reside either in the project of the targeted widget or in a separate project. The targeted widget is the widget, which you want to apply the multi-view designer to.
To create the class for the view, perform the following.
    - Add a new class to the project of the targeted widget.
    For example, name it MultiViewWidgetDesignerView.cs 
    - Add a reference to Telerik.Sitefinity assembly.
    Perform the following:
    
        - In the context menu of References, click Add Reference...
 
        - Click Browse tab and navigate to folder C:\Program Files (x86)\Telerik\Sitefinity CMS\Libraries.
 
        - Select the assembly and click OK.
 
    
     
    - Add a reference to the System.Web.Extensions assembly.
    Perform the following
    
        - In the context menu of References, click Add Reference...
 
        - Click the .NET tab, select the assembly, and click OK.
 
    
     
    - Add statement using Telerik.Sitefinity.Web.UI.ControlDesign; to the class.
 
    - Make the class to inherit the ContentViewDesignerView class.