WIX Custom Actions built for .Net Framework 4.0 does not work? Ways to resolve?

Question

We were using WIX 3.5 (Build Number 1811) and built a custom action built using Visual Studio 2008 and with target framework as .Net 3.5. This used to work great, until we built the custom action using Visual Studio 2010 and with target framework as .Net 4.0.

WIX is unable to invoke the custom action, the error that we get is this:

  SFXCA: Extracting custom action to temporary directory: C:\Windows\Installer\MSI69BD.tmp-\
    SFXCA: Binding to CLR version v2.0.50727
    Calling custom action SomeCompany.SomeProduct.InstallerPlugin!SomeCompany.SomeProduct.InstallerPlugin.XYZProductCustomAction.ABCMethod
    Error: could not load custom action class SomeCompany.SomeProduct.InstallerPlugin.XYZProductCustomAction from assembly: SomeCompany.SomeProduct.InstallerPlugin

    System.BadImageFormatException: Could not load file or assembly 'SomeCompany.SomeProduct.InstallerPlugin' or one of its dependencies. This assembly is built by a runtime newer than the currently loaded runtime and cannot be loaded.

    File name: 'SomeCompany.SomeProduct.InstallerPlugin'
       at System.Reflection.Assembly._nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, Assembly locationHint, StackCrawlMark& stackMark, Boolean throwOnFileNotFound, Boolean forIntrospection)
       at System.Reflection.Assembly.nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, Assembly locationHint, StackCrawlMark& stackMark, Boolean throwOnFileNotFound, Boolean forIntrospection)
       at System.Reflection.Assembly.InternalLoad(AssemblyName assemblyRef, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection)
       at System.Reflection.Assembly.InternalLoad(String assemblyString, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection)
       at System.AppDomain.Load(String assemblyString)
       at Microsoft.Deployment.WindowsInstaller.CustomActionProxy.GetCustomActionMethod(Session session, String assemblyName, String className, String methodName)

Answer 1

Are you expecting that the 2.0 CLR will be able to load a 4.0 assembly and execute it?

Answer 2

There is a bug open to tweak the DTF supportedRuntime element in its manifest to support NETFX 4.0. That bug hasn't been fixed yet so you need still to do it yourself.

Answer 3

Well we finally resolved the problem, we had to set:

useLegacyV2RuntimeActivationPolicy="true"
and
have both versions specified:
<supportedRuntime version="v2.0.50727"/>
and
<supportedRuntime version="v4.0"/>

If just "<supportedRuntime version="v4.0"/> is specified, it does not work. So looks like a bug in WIX 3.5 Beta

Answer 4

Additionally to the solution from Ngm we had to set the target framework of the managed custom action class library back to .NET 2.0 to get things working.