Calling referenced .NET assemblies: Could not load file or assembly

Using an DllExported-dll as a broker between VBA and other .NET code (separate dll’s) doesn’t seem to work.

How to reproduce

See attached project DllExportTest.zip

• ClassLibrary1 exposes UnmanagedExport.CreateBroker(). Works fine.
• CreateBroker returns new Class1 (from ClassLibrary1). Works fine.
• Class1.DoNothingOnClass2() creates an instance of Class2 (from ClassLibrary2) and runs a quite simple method on it.

Build de project. In a VBA-module (I used Access):

---

Declare Function CreateBroker Lib "C:\source\repos\DllExportTest\ClassLibrary1\bin\Debug\ClassLibrary1.dll" () As Object


Public Sub RunTest()
  Dim class1 As Object
  
  Set class1 = CreateBroker()
  
  class1.DoNothingOnClass2
  
  Set class1 = Nothing
End Sub

---

(be sure to correct the path in the Declare Function to point to the built dll)

Execute the RunTest()

VBA gives “'Could not load file or assembly ‘ClassLibrary2, version=1.0.0.0, Culture=neutral, PublicKeyToken=null’ or one of iets dependencies. The system cannot find the file specified.”

[bertstomphorst]

Thanx Denis, got it work with following change: In Class1.DoNothingOnClass2 (where Class2 was initialized), change body of DoNothingOnClass2() from

        public void DoNothingOnClass2()
        {
            new Class2().DoNothing();
        }

to

        public void DoNothingOnClass2()
        {
            string path = new FileInfo(Assembly.GetExecutingAssembly().Location).DirectoryName;
            var assemblyname = "ClassLibrary2";
            var typename = "Class2";

            dynamic class2 = AppDomain.CurrentDomain.CreateInstanceFromAndUnwrap($@"{path}\{assemblyname}.dll", $"{assemblyname}.{typename}");
            class2.DoNothing();
        }

After that, found that AssemblyResolve works better, because it loads all types from referenced assembly, and in ClassLibrary1 everything is typed. Solution (for others reference): static class UnmanagedExport (from sample project) should be:

    static class UnmanagedExport
    {
        static UnmanagedExport()
            => AppDomain.CurrentDomain.AssemblyResolve += CurrentDomain_AssemblyResolve;

        static Assembly CurrentDomain_AssemblyResolve(object sender, ResolveEventArgs args)
            => Assembly.LoadFrom($@"{new FileInfo(args.RequestingAssembly.Location).DirectoryName}\{args.Name.Split(',')[0]}.dll");

        [DllExport]
        [return: MarshalAs(UnmanagedType.IDispatch)]
        static object CreateBroker()
            => new Class1();
    }

[bertstomphorst]

Thank you so far Denis, I will dive into it and share my experience here