Tuesday, 18 January 2011

Enable 32-bit application pools on IIS7

The problem

I ran into the situation where a WCF service had a reference to sever 3rd party components. One of the components itself actually had a reference to some ancient 16-bit code. The WCF service was hosted in IIS7 on a 64-bit machine and used Unity to resolve dependencies.

As Unity tried to resolve dependencies I kept getting an error that looked a bit like this:

Unexpected exception thrown by call to <service type here>: Resolution of the dependency
failed, type = "<service contract interface here>", name = "(none)".
Exception occurred while: Calling constructor <type that failed construction>.
Exception is: FileNotFoundException - Could not load file or assembly <assembly name here>,
Version=, Culture=neutral, PublicKeyToken=<key here>' or one of its dependencies. 
The system cannot find the file specified.


The solution

The solution was to configure the application pool that the service was using to allow 32-bit assemblies.

1. View application pools and select the appropriate pool from the list.
2. Choose ‘Advanced settings…’ from the menu on the right.


3. Set ‘Enable 32-Bit Applications’ to True.
4. Click OK.



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