HOWTO: Create an add-in that targets several Visual Studio versions with the same add-in DLL using C# or VB.NET.

HOWTO: Create an add-in that targets several Visual Studio versions with the same add-in DLL using C# or VB.NET.

Author:	Carlos J. Quintero (Microsoft MVP)	Applies to:	Microsoft Visual Studio 2005
Date:	August 2011		Microsoft Visual Studio 2008
Updated:	October 2012		Microsoft Visual Studio 2010
			Microsoft Visual Studio 2012

Introduction

This article explains how to create an add-in that targets Visual Studio 2005 or higher using the same source code and the same output binary DLL.

More Information

To create an add-in that can target Visual Studio 2005, 2008, 2010 and 2012 using the same source code and the same output binary Dll (no conditional compilation) follow these considerations:

Use .NET Framework 2.0. Do not use .NET Framework 3.0, 3.5, 4 or 4.5.

A .NET Framework is composed of a Common Language Runtime (CLR) and some libraries:
- .NET Framework 2.0, .NET Framework 4 and .NET Framework 4.5 provide its own CLR.
- .NET Framework 3.0 and .NET Framework 3.5 only provide new libraries without introducing their own CLR, using the CLR 2.0 of the .NET Framework 2.0 instead.
Regarding Visual Studio versions:
- Visual Studio 2005 "out of the box" uses only .NET Framework 2.0. To use .NET Framework 3.0, some extensions are required to be installed.
- Visual Studio 2008 can use .NET Framework 2.0, 3.0 or 3.5 (all of them use CLR 2.0).
- Visual Studio 2010 can use .NET Framework 2.0, 3.0 or 3.5 (all of them use CLR 2.0), although they need to be installed separately, or .NET Framework 4 (uses CLR 4.0).
- Visual Studio 2012 can use .NET Framework 2.0, 3.0, 3.5 (all of them use CLR 2.0), although they need to be installed separately, or .NET Framework 4 (uses CLR 4.5) or .NET Framework 4.5 (uses CLR 4.5).
Therefore:
- Visual Studio 2005 and 2008 can use only CLR 2.0, so that discards .NET Framework 4 and 4.5.
- Visual Studio 2005 is installed by default with only .NET Framework 2.0, so that discards .NET Framework 3.0 and 3.5 (they would not be installed on a target machine with only Visual Studio 2005 without Visual Studio 2008).
- Although a machine with only Visual Studio 2010 or 2012 would not have .NET Framework 2.0 installed, assemblies compiled against .NET Framework 2.0 can run on .NET Framework 4.0 or 4.5.
Create a single project using either Visual Studio 2005, 2008, 2010 or 2012. That is, despite using .NET Framework 2.0 you are not required to use Visual Studio 2005 (or 2008 or 2010), you can use Visual Studio 2012.
Use the following references (see the article INFO: Assemblies used in Visual Studio Extensibility):
- EnvDTE
- EnvDTE80
- Extensibility
- Microsoft.VisualStudio.CommandBars
- VSLangProj
- VSLangProj2
- VSLangProj80
- VsWebSite.Interop
Do not use the following references (which are not installed by Visual Studio 2005):
- EnvDTE90
- EnvDTE90a
- EnvDTE100

VSLangProj90
VSLangProj100
VSLangProj110
VsWebSite.Interop90
VsWebSite.Interop100

The add-in can know the version of Visual Studio where it is loaded using the DTE.Version property, which returns:
- 8.0 for Visual Studio 2005
- 9.0 for Visual Studio 2008
- 10.0 for Visual Studio 2010
- 11.0 for Visual Studio 2012
To register the add-in for Visual Studio using XML registration (.AddIn file) (see the article INFO: Default .AddIn file locations for Visual Studio add-ins) you can:
- Use a single .AddIn file in a common folder for all Visual Studio versions (such as "%ALLUSERSPROFILE%\Application Data\Microsoft\MSEnvShared\AddIns" to register the add-in for all users, or "%APPDATA%\Microsoft\MSEnvShared\AddIns" to register the add-in for the current user). The .AddIn file must specify all host Visual Studio versions that it targets:
  
  <Extensibility xmlns="http://schemas.microsoft.com/AutomationExtensibility">
      <HostApplication>
          <Name>Microsoft Visual Studio</Name>
          <Version>11.0</Version>
      </HostApplication>
      <HostApplication>
          <Name>Microsoft Visual Studio</Name>
          <Version>10.0</Version>
      </HostApplication>
      <HostApplication>
          <Name>Microsoft Visual Studio</Name>
          <Version>9.0</Version>
      </HostApplication>
      <HostApplication>
          <Name>Microsoft Visual Studio</Name>
          <Version>8.0</Version>
      </HostApplication>
      <Addin>
          ...
      </Addin>
  </Extensibility>
- Use a different .AddIn file in a folder specific for each Visual Studio version (such as "%VSCOMMONAPPDATA%\AddIns" to register the add-in for all users or "%VSAPPDATA%\AddIns" or "%VSMYDOCUMENTS%\AddIns" to register the add-in for the current user).
The add-in can know the registry key of the Visual Studio where it is loaded using the DTE.RegistryRoot property, which returns:
- "Software\Microsoft\VisualStudio\8.0" for Visual Studio 2005
- "Software\Microsoft\VisualStudio\9.0" for Visual Studio 2008
- "Software\Microsoft\VisualStudio\10.0" for Visual Studio 2010
- "Software\Microsoft\VisualStudio\11.0" for Visual Studio 2012
The add-in can store settings common to all Visual Studio versions in a registry key such as HKEY_CURRENT_USER\Software\<add-in>, or settings specific to a Visual Studio version in registry keys such as HKEY_CURRENT_USER\Software\<add-in>\VS2005, HKEY_CURRENT_USER\Software\<add-in>\VS2008, etc.
Since the add-in targets several Visual Studio versions with the same binary dll, the setup of the add-in does not require to detect which versions of Visual Studio are installed. The add-in can be registered even for Visual Studio versions that are not installed (specially when using a single .AddIn XML registration file, as explained above).

Go back to the 'Resources for Visual Studio .NET extensibility' section for more articles like this

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