We have a number of applications running under a single IIS site, but one needs to run in a 32-bit application pool due to an old library it uses.

However, we can't currently do this because there are two 64-bit ISAPI filters set up on the parent site, which means IIS spits out a Calling LoadLibraryEx on ISAPI filter error when you try to access the application running in the 32-bit app pool.

I've found the <isapiFilters> config element (reference), but adding this to the application's web.config with <remove> elements for each of the filters I want to disable doesn't do anything:

    <remove name="FILTER_1_NAME" />
    <remove name="FILTER_2_NAME" />

I don't really want to disable these filters for all the apps running under this site, just for the sake of this one.

Is there any way to do this at the application level?


No, according to the documentation, isapiFilters can only be defined on the server or site level.

You may put the 32bit Application into its own site and then URL-rewrite every request for it from the main site. But that may result into more problems/work depending on your application.

  • Ah, missed that the first time—having re-read the docs I see now, thanks! – Mark Bell Jan 30 '15 at 12:19

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