Hi,
the DLL is compiled to v2.0.50727 of .NET, your project is .NET 4.0.
you need to set mixed mode assembly in app.config.
="1.0"
<configuration>
<startup useLegacyV2RuntimeActivationPolicy="true">
<supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.0"/>
</startup>
</configuration>
With best Regards.