Visual Studio 2008 SP1 and ReSharper 4.1 were happily running and helping me develop software, but I wanted to try out the early drops of ReSharper 4.5, which you can find here. I didn’t want to disturb my existing install. So I went looking for a way to run ReSharper 4.1 and 4.5 side-by-side. JetBrains provides the following installation notes, which gave a glimmer of hope.

http://www.jetbrains.net/confluence/display/ReSharper/Installation+Notes+for+ReSharper

Let me start off by saying that I don’t have any meaningful experience building add-ins for Visual Studio. Everything below was gleaned from JetBrains and MSDN documents. Having gone through the trouble, I wouldn’t recommend this approach due to certain – apparently inherent – limitations. (The biggest limitation is that you can only run Visual Studio from the experimental hive as an administrator. The RANU switches might give you a glimmer of hope, but JetBrains would have to update its install utility to support it, as far as I can tell.)

Honestly, turn back now! It’s not worth the trouble. If you’re really concerned about the cleanliness of your Visual Studio install, I would recommend installing VS2008 and ReSharper 4.5 in a virtual machine. If not, then I would recommend uninstalling ReSharper 4.1, installing ReSharper 4.5, and tolerating any glitches in the early builds. The occasional glitch is probably going to be less annoying than the instructions below!

Remember: ReSharper 4.5 builds are daily builds of a product that is in active development. JetBrains is very upfront about the quality of builds on their daily builds page. Whichever method you choose – experimental hive or regular install – be prepared to upgrade to a later build on at least a weekly or biweekly basis.

Oh, you’re still here. I guess you really want to know about how to install ReSharper into an experimental Visual Studio hive. Don’t say I didn’t warn you.

Let’s take a journey into the black art of Visual Studio add-in development… If you’re developing an add-in for Visual Studio, how the heck do you develop and debug it safely. How do you develop in one copy of Visual Studio and use it to debug another copy of Visual Studio running your plug-in? You use experimental Visual Studio hives. Visual Studio hives are areas of the Windows registry that Visual Studio uses to store configuration information. Visual Studio uses the key HKLM\SOFTWARE\[Wow6432Node]\Microsoft\VisualStudio\9.0 to store its default hive. (If you’re running 64-bit Windows, configuration information is stored beneath the Wow6432Node because Visual Studio 2008 is a 32-bit program. If you’re running 32-bit Windows, the registry path doesn’t contain the Wow6432Node.) If you install into an experimental hive, a suffix is appended to the registry path. For example, we’ll be using an experimental hive called ReSharper. So the registry path is HKLM\SOFTWARE\[Wow6432Node]\Microsoft\VisualStudio\9.0ReSharper. When you launch Visual Studio, you can direct it to the default hive (launch VS normally) or an experimental hive via:

devenv /RootSuffix ReSharper

You can have as many experimental hives as you like. This leaves you free to try out different add-ins, ReSharper or otherwise, in a relatively isolated fashion. The choice of “ReSharper” as my experimental hive name is completely arbitrary. I could just as easily called it Ickyickyickyickypatangzoopboing. (Bonus points if you can place the experimental hive name.) 🙂

Please note that you’ll be mucking around with your registry and in particular, your Visual Studio install. If things go really badly, you could have to re-install Visual Studio or even your OS. Probably not, but this is an unsupported install mode. Use the same care as directly editing your Windows Registry (which is essentially what you’re doing). I’m not responsible for any damage you may cause. No warranty express or implied. Do not wash in hot. Objects in mirror may be closer than they appear…

You’ll need to download the Visual Studio 2008 SDK 1.1 – the version of the SDK for Visual Studio 2008 SP1. (It would have been too easy to call it the Visual Studio 2008 SP1 SDK.) You can find it here. The SDK contains tools for managing experimental Visual Studio hives. The one that we’ll need is called VsRegEx, which is a command line tool for creating, modifying, and deleting experimental Visual Studio hives. We’ll be creating an experimental hive called ReSharper by copying our default hive.

Open a Visual Studio 2008 Command Prompt as an administrator. (Shift-right-click on Visual Studio 2008 Command Prompt, Run as… Administrator.)

cd C:\Program Files (x86)\Microsoft Visual Studio 2008 SDK\VisualStudioIntegration\Tools\Bin
VsRegEx GetOrig 9.0 ReSharper

Be patient. This might take a minute or two. (If you want to delete the experimental hive later, run “VsRegEx Delete 9.0 ReSharper”. Note the space between 9.0 and ReSharper.)

Download and install your preferred daily build of ReSharper 4.5. IMPORTANT: When installing, make sure you disable all Visual Studio integration. We’ll be performing the integration manually in the next step.

Copying InstallExperimentalHive.Proj to the Bin directory of your ReSharper install location. (Mine is at C:\Program Files (x86)\JetBrains\ReSharper\v4.5\Bin).

cd C:\Program Files (x86)\JetBrains\ReSharper\v4.5\Bin
msbuild InstallExperimentalHive.Proj /t:Rebuild
devenv /RootSuffix ReSharper /Setup

Be patient. The last step might take a few minutes.

Create a shortcut to “devenv /RootSuffix ReSharper” on your desktop and mark the shortcut to run as an administrator. (Right-click the shortcut… Properties… Shortcut tab… Advanced… Run as administrator.) Double-click the shortcut and you should see:

So there you have it. ReSharper 4.5 running in an experimental Visual Studio hive. If you install a new daily build of ReSharper 4.5, you won’t have to recreate the hive, but you may have to msbuild and devenv /Setup steps above. Have fun with trying out ReSharper 4.5!