visual studio 2010 – Why can’t IronPython find my VS2010 VB.Net class library DLL – Education Career Blog

I created a Class Library project in Visual Studio 2010 and created added the following VB.Net class:

Public Class Dumb
    Private name As String

    Public Sub New(ByVal newName As String)
        name = newName
    End Sub

    Public Sub sayHi()
        System.Console.WriteLine("Hi " & name)
    End Sub
End Class

I built the solution and generated a DLL file (say PATH_TO_NEW_DLL).

In IronPython, I get the error below when I try to clr.AddReferenceToFileAndPath(PATH_TO_NEW_DLL). The file DOES exist on my computer.

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
IOError: System.IO.IOException: file does not exist: PATH_TO_NEW_DLL
   at IronPython.Runtime.ClrModule.AddReferenceToFileAndPath(CodeContext context, String file)
   at IronPython.Runtime.ClrModule.AddReferenceToFileAndPath(CodeContext context, String files)
   at Microsoft.Scripting.Utils.ActionHelper`2.Invoke(Object arg0, Object arg1)
   at Microsoft.Scripting.Utils.ReflectedCaller.Invoke(Object args)
   at Microsoft.Scripting.Actions.Calls.MethodCandidate.Caller.Call(Object args, Boolean& shouldOptimize)
   at IronPython.Runtime.Types.BuiltinFunction.BuiltinFunctionCaller`2.Call1(CallSite site, CodeContext context, TFuncType func, T0 arg0)
   at System.Dynamic.UpdateDelegates.UpdateAndExecute3T0,T1,T2,TRet(CallSite site, T0 arg0, T1 arg1, T2 arg2)
   at <unnamed>$28.<unnamed>(CodeContext $globalContext, FunctionCode functionCode) in <stdin>:line 1
   at IronPython.Compiler.PythonScriptCode.RunWorker(CodeContext ctx)
   at IronPython.Compiler.PythonScriptCode.Run(Scope scope)
   at IronPython.Hosting.PythonCommandLine.<>c__DisplayClass1.<RunOneInteraction>b__0()


Use a relative path to your startup file. Here is an example:

In one of my projects, the startup file (the one that has the green “play” icon in your solution explorer) was in a folder that had another folder PMX in it. Inside the PMX folder was the DLL I was trying to access. This DLL had the PMXlib namespace in it. The PMXlib namespace had a class called “PMX“.
So, the directory structure is as follows:


This is the code I used to access the PMX class inside the PMXlib DLL.

import clr
from PMXlib import PMX 
#PMXlib is the namespace name. PMX is the class name inside the DLL.

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