text: ---
  title: "Registering Extensions of the .NET Framework | Microsoft Docs"
  ms.date: 11/15/2016
  ms.prod: "visual-studio-dev14"
  ms.technology: msbuild
  ms.topic: conceptual
  helpviewer_keywords: 
    - "Add References dialog box, registering extensions of the .NET Framework"
    - "MSBuild, registering extensions of the .NET Framework"
    - ".NET Framework extensions, registering"
  ms.assetid: deee6f53-ea87-4b88-a120-bea589822e03
  caps.latest.revision: 8
  author: mikejo5000
  ms.author: mikejo
  manager: jillfra
  ---
  # Registering Extensions of the .NET Framework
  [!INCLUDE[vs2017banner](../includes/vs2017banner.md)]
  
  You can develop an assembly that extends a specific version of the .NET Framework. To enable the assembly to appear in the Visual Studio **Add References** dialog box, you must add the folder that contains it to the system registry.  
    
   For example, assume that the Trey Research company has developed a library that extends the .NET Framework 4, and wants the library assemblies to appear in the **Add References** dialog box when a project targets the .NET Framework 4. Also assume that the assemblies are 32-bit assemblies running on a 32-bit computer or 64-bit assemblies running on a 64-bit computer, and that they will be installed in the C:\TreyResearch\Extensions4\ folder.  
    
   Register this folder by using this key: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\\.NETFramework\v4.0.21006\AssemblyFoldersEx\TreyResearch\\. Give the key this default value: C:\TreyResearch\Extensions4.  
    
  > [!NOTE]
  > The build number of the .NET Framework version may be different.  
    
   To register a 32-bit assembly on a 64-bit computer, use the Wow6432 node, for example: HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\\.NETFramework\v4.0.21006\AssemblyFoldersEx\TreyResearch\\.  
    
  ## See Also  
   [Visual Studio Integration](../msbuild/visual-studio-integration-msbuild.md)
  