Microsoft SMO for .Net 4.0

I am creating a setup project for a product. For my install, I have an executable that is run as a custom action. This executable is responsible for executing a SQL script during the install. However the SMO is giving me the following error:

Mixed mode assembly is built against version 'v2.0.50727' of the runtime

Most responses from google have told me to put the following in my app.config file, which I did but it didn't seem to solve the problem.

  <startup us开发者_如何学GoeLegacyV2RuntimeActivationPolicy="true">
    <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.0"/>
  </startup>

Anybody have any solutions.