ASP.NET MVC 3 can be installed side by side with ASP.NET MVC 2 on the same computer, which gives you flexibility in choosing when to upgrade an ASP.NET MVC 2 application to ASP.NET MVC 3.

To manually upgrade an existing ASP.NET MVC 2 application to version 3, do the following:

1. Create a new empty ASP.NET MVC 3 project on your computer. This project will contain some files that are required for the upgrade.
2. Copy the following files from the ASP.NET MVC 3 project into the corresponding location of your ASP.NET MVC 2 project. You'll need to update any references to the jQuery library to account for the new filename ( jQuery-1.5.1.js):
   • /Views/Web.config
   • /packages.config
   • /scripts/*.js
   • /Content/themes/*.*
3. Copy the packages folder in the root of the empty ASP.NET MVC 3 project solution into the root of your solution, which is in the directory where the solution’s .sln file is located.
4. If your ASP.NET MVC 2 project contains any areas, copy the /Views/Web.config file to the Views folder of each area.
5. In both Web.config files in the ASP.NET MVC 2 project, globally search and replace the ASP.NET MVC version. Find the following:

   System.Web.Mvc, Version=2.0.0.0

   Replace it with the following:

   System.Web.Mvc, Version=3.0.0.0

6. In Solution Explorer, delete the reference to System.Web.Mvc (which points to the DLL from version 2), then add a reference toSystem.Web.Mvc (v3.0.0.0).
7. Add a reference to System.Web.WebPages.dll and System.Web.Helpers.dll. These assemblies are located in the following folders:
   • %ProgramFiles%\ Microsoft ASP.NET\ASP.NET MVC 3\Assemblies
   • %ProgramFiles%\ Microsoft ASP.NET\ASP.NET Web Pages\v1.0\Assemblies
8. In Solution Explorer, right-click the project name and select Unload Project. Then right-click the project name again and select Edit ProjectName.csproj.
9. Locate the ProjectTypeGuids element and replace {F85E285D-A4E0-4152-9332-AB1D724D3325} with {E53F8FEA-EAE0-44A6-8774-FFD645390401}.
10. Save the changes, right-click the project, and then select Reload Project.
11. In the application’s root Web.config file, add the following settings to the assemblies section.

    <add assembly="System.Web.WebPages, Version=1.0.0.0, Culture=neutral,
    
         PublicKeyToken=31BF3856AD364E35" />
    
    <add assembly="System.Web.Helpers, Version=1.0.0.0, Culture=neutral,
    
         PublicKeyToken=31BF3856AD364E35" />

12. If the project references any third-party libraries that are compiled using ASP.NET MVC 2, add the following highlightedbindingRedirect element to the Web.config file in the application root under the configuration section:

    <runtime>
    
       <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
    
         <dependentAssembly>
    
           <assemblyIdentity name="System.Web.Mvc"
    
               publicKeyToken="31bf3856ad364e35"/>
    
           <bindingRedirect oldVersion="1.0.0.0-2.0.0.0" newVersion="3.0.0.0"/>
    
         </dependentAssembly>
    
       </assemblyBinding>
    
    </runtime>