How can I force IIS Express to run in 32 bit mode?

Question

I have a classic ASP app that I'm trying to run under IIS Express on 64 bit Windows. It uses Jet to connect to a Microsoft Access database and will not work under 64 bit.

I have created the following application pool for the ASP app, but it seems to ignore the enable32BitAppOnWin64 attribute and the process is still 64 bit.

<applicationPools>
    <add name="UnmanagedClassicAppPool32" managedRuntimeVersion="" managedPipelineMode="Classic" autoStart="true" enable32BitAppOnWin64="true" />
</applicationPools>

How can I get this app pool in IIS Express to run as a 32 bit process?

score 152 · Answer 1 · edited Jun 14 '23 at 06:44

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For Visual Studio 2013, Visual Studio 2015, Visual Studio 2017, Visual Studio 2019, Visual Studio 2022:

 Tools
  -> Options
   -> Projects and Solutions
    -> Web Projects
     -> Uncheck "Use the 64 bit version of IIS Express for web sites and projects"`

edited Jun 14 '23 at 06:44

Ra.

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answered May 13 '15 at 03:39

Neal

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Thanks Neal! I had mine defaulted to run as 64 bit for some reason and that got me seriously wondering why it's using GAC_64 libraries even though the target platform was set to x86. – InitialV Jun 05 '15 at 04:44
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These directions hold true for Visual Studio 2015 as well! – Jim Buck Oct 08 '15 at 15:18
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This works globally. Is there a way to do this per-project? – arni Aug 10 '16 at 08:30
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I had the opposite problem, this was unchecked and I was trying to run a 64-bit project. Checking it fixed the issue. Thanks! – Andacious Nov 22 '16 at 17:46
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True for Visual Studio 2017 – Dimskiy Jul 24 '17 at 16:49
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works also for vs2022 – Noam Jan 16 '22 at 15:14
I didn't think that it was the IIS Express that was causing the IM002 error. I spent 2 days tinkering the Configuration Manager and scouring the web to get the app to operate on x86. – Denny Jacob Apr 14 '23 at 05:03

score 45 · Accepted Answer · edited May 23 '17 at 12:26

45

According to this, IIS Express 7.5 comes only as a 32 bit application. IIS Express 8.0 however, comes with both 32 bit and 64 bit versions of the application. The 32 bit version can be found at c:\program files (x86)\IIS Express\iisexpress.exe and the 64 bit version can be found at c:\program files\IIS Express\iisexpress.exe.

IIS Express ignores the enable32BitAppOnWin64 attribute. To run the app pool as 32 bit, you must execute the 32 bit version of IIS Express.

You can determine which version is running in Task Manager by examining the process on the Processes tab. The 64 bit version will be displayed as iisexpress.exe and the 32 bit version will be displayed as iisexpress.exe *32.

edited May 23 '17 at 12:26

Community

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answered Apr 26 '13 at 00:29

John Mills

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Good advice, was trying to fix a build on our build server after an upgrade for a full day yesterday and the change from IIS 7.5-8 was the issue. – jcvandan May 21 '13 at 08:44
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Use the following command, which uses a junction to force IISExpress to use the 32-bit version: `mklink /j "c:\program files\IIS Express\" "c:\program files (x86)\IIS Express\"` – Banoona Nov 18 '14 at 17:29

score 8 · Answer 3 · answered Mar 21 '21 at 17:31

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Add <Use64BitIISExpress>false</Use64BitIISExpress> under the <PropertyGroup> tag of your csproj project.

It's also available through the UI by clicking on project properties -> Web tab -> Bitness (change to x64).

answered Mar 21 '21 at 17:31

BornToCode

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score 2 · Answer 4 · answered Nov 18 '14 at 06:52

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In IIS Express property window of VS studio, change the first option: 'Managed Application Pool' from 'Integrated' to 'Classic'

answered Nov 18 '14 at 06:52

Paul

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score 1 · Answer 5 · answered Oct 01 '14 at 07:54

Are you sure?

It uses Jet to connect to a Microsoft Access database and will not work under 64 bit.

I had the same problem and eventually solved it by forcing the 64 bit drivers to install. Initially that failed because of an error that you can't install the 64 bit drivers if you have Office 2010 32 bit installed.

But ... you can force the 64 bit version of the Access Database Engine (ACE) from here to install with the 'passive' switch:

AccessDatabaseEngine_x64.exe /passive

And then I was able to run my legacy code with my current development environment.

How can I force IIS Express to run in 32 bit mode?

5 Answers5

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