wixsharp: Projects with CustomActions failing to build

Any project including a CustomAction seems to fail. My own project looks like this:

using System;
using System.IO;
using System.Windows.Forms;
using Microsoft.Deployment.WindowsInstaller;
using WixSharp;

namespace Installer
{
    class Program
    {
        static void Main()
        {
            var project = new Project("Test",
                new Dir(@"%ProgramFiles%\Test",
                    new DirFiles(@"C:\Test\*.*")),
                new Dir(@"%ProgramMenu%",
                    new ExeFileShortcut("Test", Path.Combine("[INSTALLDIR]", "Launcher.exe"),
                            arguments: "")
                        { WorkingDirectory = "[INSTALLDIR]" }),
                new ManagedAction(CustomActions.MyAction));

            project.GUID = new Guid("93fefff9-91b2-4c44-8b13-9aad00c8f6a3");
            project.Platform = Platform.x64;
            project.Version = new Version(2, 0, 0, 0);
            project.UI = WUI.WixUI_ProgressOnly;
            project.MajorUpgradeStrategy = MajorUpgradeStrategy.Default;

            project.BuildMsi();
        }
    }

    public static class CustomActions
    {
        [CustomAction]
        public static ActionResult MyAction(Session session)
        {
            MessageBox.Show("Test", "Test");//Environment.GetCommandLineArgs().ConcatItems(" "));
            session.Log("Begin MyAction Hello World");

            return ActionResult.Success;
        }
    }
}

Also, I tried building the AdminInstall sample in Visual Studio, which also fails to build. Still a problem with the VS integration?