Deploying on AppHarbor throwing Mixed Mode Assembly error

Question

We are trying out AppHarbor, but are getting a build error as follows:

SGEN : error : Mixed mode assembly is built against version 'v2.0.50727' of the runtime and cannot be loaded in the 4.0 runtime without additional configuration information.

This was the first time we had seen this pop up, and after some searching it looks like we need to add the following snippet to the config:

<startup useLegacyV2RuntimeActivationPolicy="true"> 
        <supportedRuntime version="v4.0" />      
</startup>

However, it sounds like this needs to be added to the WebDev.WebServer40.exe.config, not our applications config file.

How could we do this on AppHarbor?

Answer 1

Have you tried setting Generate serialization assembly to "Off" as suggested in this question?