Upgrade from Sitefinity CMS 8.0
If your project is running on Sitefinity 8.0, to upgrade it, perform the following:
    - Backup your project and its database.
 
    - Uninstall 
Telerik.Sitefinity.All package. 
    If you have Telerik.Sitefinity.All package installed, remove the package and all its dependencies:
    
        - Open your project in Visual Studio
 
        - Open the context menu of your solution, click Manage NuGet Packages...
 
        - In the list of installed packages, find 
Telerik.Sitefinity.All, click Uninstall, and press ENTER to close the dialog. 
    
     
    - Set the target framework version of your project to .Net Framework 4.7.2.
    Perform the following:
    
        - Open your project in Visual Studio.
 
        - In the context menu of SitefinityWebApp, click Properties.
 
        - On Application tab, in Target framework dropdown box, select .NET Framework 4.7.2
 
        - Save the changes to your project
 
    
     
    - Reinstall all packages:
    
        - In Visual Studio, navigate to Tools » Library Package Manager » Package Manager Console.
 
        - Execute the following command: Update-Package -Reinstall
        
 NOTE: You do this, because the changing the target framework requires re-installation of all packages. After you have removed all Sitefinity CMS related packages in Step 2, you perform this step to re-install all other packages that you may have installed on your system.
         
    
     
    - From the 
bin folder of the project, delete Telerik.Sitefinity.UI.MVC.dll. 
    - Open folder 
Properties, located in your project's folder and edit the AssemblyInfo.cs file.
    Add the following assemblies:
    
        - [assembly: Telerik.Sitefinity.Frontend.Mvc.Infrastructure.Controllers.Attributes.ControllerContainer]
 
        - [assembly: Telerik.Sitefinity.Frontend.Mvc.Infrastructure.Controllers.Attributes.ResourcePackage]
 
    
     
    - In the Package Manager Console install 
Telerik.Sitefinity.All 12.1.7100.0 using the following command:
     Install-Package Telerik.Sitefinity.All –Version 12.1.7100.0 
     NOTE: The BCL dependency used by Sitefinity CMS to integrate Azure search in previous versions is also removed. As a result, you can safely remove the Tools folder under the root of your SitefinityWebApp project. 
     
    - In the Package Manager Console, uninstall the following packages and delete the respective assemblies from the project's 
bin folder:
    
        Telerik.Sitefinity.Thunder 
        Telerik.Sitefinity.DropboxLibraries 
        Telerik.Sitefinity.MobileAppBuilder 
        Telerik.Sitefinity.DAM 
        Telerik.Sitefinity.EverliveConnector 
    
     
    - Build your solution.