C# WiX Custom Actions crash with "Could not load file or assembly"

[ERGeorgiev]

I have a C# WiX project, like this (trimmed code):
C# WiX project Main:

public class WixInstaller
{
    public static void Main()
    {
        // Setup Project
        var project = new Project(AppName,
            // Application Dir
            new Dir(@$"%ProgramFiles%\{AppName}",
                // Application Files
                new Files($@"{binPath}\*.*"),
                // Program Menu Exe
                new File($@"{binPath}\{AppName}.exe",
                    new FileShortcut(AppName, @$"%ProgramMenu%\{AppName}") { IconFile = iconPath }))
        );

        // Run After Install
        var runAfterInstallAction = new ElevatedManagedAction(
            CustomActions.RunAfterInstall, Return.check, When.After, Step.InstallFinalize, Condition.NOT_Installed) 
        { 
            Execute = Execute.immediate 
        };
        project.AddAction(runAfterInstallAction);

        Compiler.BuildMsi(project, System.IO.Path.Combine(_solutionDirectory, fileName));
    }
}

The custom action:

public class CustomActions
{
    [CustomAction]
    public static ActionResult RunAfterInstall(Session session)
    {
        try
        {
            // This pattern in necessary to catch exceptions relating to missing dlls.
            Action(session);
        }
        catch (Exception e)
        {
            MessageBox.Show(e.Message);
        }

        return ActionResult.Success;

        static void Action(Session session)
        {
            using Microsoft.Win32.TaskScheduler.TaskService ts = new();
        }
    }
}

When the custom action is executed, it errors out in Could not load file or assembly Microsoft.Win32.TaskScheduler version..... I am not sure how to fix this. There's a lot of guides available online, but seems like there's nothing on a WiX C# project, even on WiX's actual documentation. Seems like I need to add a dll file referenced by the action, but the C# project doesn't seem to have similar functionality.

• I tried project.AddBinary(), but it didn't fix the issue.
• I tried setting the custom action's actionAssembly to the required binary with no luck (couldn't find it, seems like no CA file was being created)
• Making a separate project for customActions
• project.DefaultRefAssemblies.Add(typeof(TaskScheduler).Assembly.Location);
• Specifying actionAssembly typeof(CustomActions).Assembly.Location

[oleg-shilo]

The correct way of embedding CA dependencies is to add them with project.DefaultRefAssemblies.Add.
This will ensure that the MakeSfxCA packages them with your CA assembly. So you have done it right.

Is there any chance that you are embedding an x64 version of assembly (check it in the assembly file). Because if you are then it cannot load to MSI runtime that is always a x86 CPU.

If it does not help then I can only suggest the debugging. Isolate your working code in a separate method and call it from the CA body. Before the call subscribe for the AppDomain.CirrentDomain.ResolveAssembly event. Then fire the assertion on the entry in CA (see wiki for debugging steps). This will tell you what are the other dependencies that are missing.

[oleg-shilo]

I just tested and it seems to work just fine:

[ERGeorgiev]

project.DefaultRefAssemblies.Add(@".\bin\Debug\net472\Microsoft.Win32.TaskScheduler.dll"); for me throws
System.IO.DirectoryNotFoundException: 'Could not find a part of the path 'C:\Users\user\Projects\VisualStudio\project\project.Installer\bin\Debug\net472\bin\Debug\net472\Microsoft.Win32.TaskScheduler.dll'.'

What worked:
project.DefaultRefAssemblies.Add(@".\Microsoft.Win32.TaskScheduler.dll");

Thank you! I am unsure why my original code was not working:
project.DefaultRefAssemblies.Add(typeof(TaskScheduler).Assembly.Location);, I assume the Location does not hold the actual .dll, but it did build the msi so I assume it did.

[oleg-shilo]

Yep, the Assembly.Location property can be empty. Though I always try to use it as it is so convenient :)