Question

I’m writing a .NET 3.5 application (WinForms) which uses classes from an external DLL and I keep receiving a System.TypeLoadException every time the application tries to start.
Here is the exception VS displays:

System.TypeLoadException was unhandled
  Message=Could not load type 'PolyMorph.Common.Settings' from assembly 'PolyMorph, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'.
  Source=PolyMorph
  TypeName=PolyMorph.Common.Settings
  StackTrace:
       at PolyMorphApp.App.Initialize()
       at PolyMorphApp.App.Main()
       at System.AppDomain._nExecuteAssembly(Assembly assembly, String[] args)
       at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
       at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
       at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       at System.Threading.ThreadHelper.ThreadStart()
  InnerException: 

Here is the code that I’m running:

Friend NotInheritable Class App

    <STAThread()> Shared Sub Main()
        'set the exception handlers'
        Application.SetUnhandledExceptionMode(UnhandledExceptionMode.CatchException)
        AddHandler AppDomain.CurrentDomain.UnhandledException, AddressOf UnhandledExceptionHandler
        AddHandler Application.ThreadException, AddressOf ThreadExceptionHandler
        'initialize the application'
        App.Initialize()

        'and then run the application'
        Dim mainForm As New PolymorphHost
        Application.Run(mainForm)
    End Sub

    Shared Function Initialize() As FunctionResult
        If App.InitializeDataDirectory() = False Then
            Return New FunctionResult(False, "the application's data directory")
        End If


        _settings = New PolyMorph.Common.Settings(AppDataDirectory & "\Settings.dat")
        ......code continues to load settings from the _settings variable
    End Function
End Class

What surprises me is that the VS2010 Debugger stops on the line App.Initialize() without even stepping into the Initialize function.

If, however, I comment out all references to the external DLL in the Initialize function, the application initializes properly.

---

After reading around, I realized that a number of people reporting this error were using different builds on their projects (as in x64 DLL being referenced from an x86 application). I therefore changed the build configuration so the DLL and the application were both x86 but I still have the TypeLoadException.

Is there anything I’m missing?

Answer 1

It appears one Nutzy also had a similar problem and he solved it by copying all the classes, forms and controls to a new project. I did likewise and the problem was solved.

Thanks, Jim Mischel and Paul Alexander for your assistance. I voted you up for your efforts to help me solve the problem.