How to run VS 2010 Local IIS in 32 bit mode

Question

I have referenced some 32 bit and some 64 bit DLL in my ASP.NET MVC 3 project.

The projects compile but I get runtime errors.

It\'s because I am running the

Answer 1

IIS Express 7.5 (as used by Visual Studio 2010 if you install it) is 32 bit only:

http://learn.iis.net/page.aspx/1265/iis-75-express-readme/

To quote:

Both 32-bit and 64-bit systems are supported, however only a 32-bit build of IIS 7.5 Express exists.

So I can't imagine that your problems would be related to the usual 32bit / 64bit pool mode issues that can arise if all of your DLL's are 32bit.

However if you're trying to load a 64 bit COM DLL then this will fail; 64 binaries can't be loaded into a 32 bit process and vice versa.

Another gotcha is forgetting to tick the Use IIS Express checkbox when choosing which web server to debug with:

If you don't tick that checkbox then you'll run your site in a child application in the DefaultWebSite on the version of IIS7 that ships with Windows.

The DefaultWebSite runs in the DefaultAppPool, which in 64 bit versions of Windows runs as a 64 bit process. So you need to change the DefaultAppPool to run as 32 bit if you want to use this instead and consume 32 bit binaries.

You need to do this using IIS7's MMC snap-in or by running the appcmd.exe tool from the command line.

Answer 2

If you don't require the 64 bit component (not sure what is running there or if this can be excluded as you simply wanted to know how to run in 32 bit more)

http://learn.iis.net/page.aspx/201/32-bit-mode-worker-processes/

You can set it at the server level via: %windir%\system32\inetsrv\appcmd set config -section:applicationPools -applicationPoolDefaults.enable32BitAppOnWin64:true

Or set your particular app pool (more recommended imho) you can try the following. Sorry the page this came from is no longer seemingly active and only googles caches is showing it now:

Force IIS to create a 32-bit app pool worker process

If your application is running as a web app, meaning it is running in an IIS app pool worker process, you’ll want that worker process (w3wp.exe) to be a 32-bit process. That can be specified in the advanced settings of the app pool:

Select the app pool for your web app. Click Advanced Settings… under Edit Application Pool on the right. Change the value of Enable 32-Bit Applications under (General) to True.

Note that the word “Enable” in the setting doesn’t mean “allow” as in “allow either 32- or 64-bit applications.” It actually means “force” as in “force the worker process to run in 32-bit mode so that 32-bit applications are supported.” This means that the app pool worker process will always be launched as a 32-bit process when this setting has a value of True. Setting it to False will launch a 64-bit app pool worker process.

Note that when an app pool worker process is started, it shows up in the Image Name column on the Processes tab in Task Manager as w3wp.exe. When the Enable 32-Bit Applications setting has a value of True, it will be listed as w3wp.exe *32.

Answer 3

Set your compile target to x86 instead of AnyCPU or x64. Your dll will always run in 32-bit without you needing to mess with the IIS server settings.