Error dynamically invoking vb.net dll from C# test application

  • Thread starter Thread starter Guest
  • Start date Start date
G

Guest

Hi all,
I have test application written in C# from which I am trying to dynamically
invoke a DLL. I have two dll's the only difference being one is written in C#
and the other in VB.NET. The test application is able to sucessfully invoke
the dll written in C#. However when attempting to invoke the VB.NET version
of the dll the following error message occurs:

Unhandled Exception: System.ArgumentNullException: Value cannot be null.
Paramater name: Type at System.Activator.CreateInstance(Type type, Boolean
nonPublic) at ConsoleApplication1.Program.Main(String[] args ) line 30.


Would anyone have any ideas why this is occuring? any help / comments
greatly appreicated (please see source code below).



TEST APPLICATION
============
using System;
using System.Collections.Generic;
using System.Text;
using System.Diagnostics;
using System.Runtime.InteropServices;
using System.Reflection;

namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{

string className = "proclaim";
string enServer = "http://gis/mcity";
string enXML = "100.xml";

//string className = "enIntegration";
string appdll = className + ".dll";
object i = null;

//use reflection to invoke the Translator component
// Load the generated assembly into the ApplicationDomain
Assembly asm = Assembly.LoadFrom(appdll);

Type mm = asm.GetType(className + "." + className);

object o = Activator.CreateInstance(mm);

//Invoke a non-static method with parameters
object[] par = new object[] { enServer, enXML };

i = (String)mm.InvokeMember("Translate", BindingFlags.Default |
BindingFlags.InvokeMethod, null, o, par);
Console.WriteLine(i);
}
}
}
C# version of DLL
==========
using System;
using System.Collections.Generic;
using System.Text;

namespace proclaim
{
class proclaim
{

public string Translate(string enServer,string enXML)
{
return "Success";
}
}
}

VB.NET version of dll
==============
Imports System
Imports System.Collections.Generic
Imports System.Text

Namespace proclaim
Class proclaim

Public Function Translate(ByVal enServer As String, ByVal enXML As
String) As String
Return "Success"
End Function
End Class
End Namespace
 
Lorraine said:
Hi all,
I have test application written in C# from which I am trying to dynamically
invoke a DLL. I have two dll's the only difference being one is written in C#
and the other in VB.NET. The test application is able to sucessfully invoke
the dll written in C#. However when attempting to invoke the VB.NET version
of the dll the following error message occurs:

Unhandled Exception: System.ArgumentNullException: Value cannot be null.
Paramater name: Type at System.Activator.CreateInstance(Type type, Boolean
nonPublic) at ConsoleApplication1.Program.Main(String[] args ) line 30.


Would anyone have any ideas why this is occuring? any help / comments
greatly appreicated (please see source code below).
Click to expand...

Well, the exception shows that Assembly.GetType has returned null. My
guess is that your VB.NET project has a "default namespace" which it
puts everything under - so your class isn't actually proclaim.proclaim,
but ProjectName.proclaim.proclaim. (I hope you don't really use the
same name for the namespace and the class, by the way - it's a really
bad idea.)
 
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