Explicit (runtime) DLL linking with Visual Basic 2013 Fails - vb.net

Question

I wrote a dll in Visual Basic on Visual Studio 2013 (what it does is irrelevant now):
Namespace TextFiles
Public Class ConfigTextFiles
'Library of functions to handle configuration text files holding pairs of parm-name, param-value.
'Param-name and Param-value are separated by the Delimiter property, or "=" if not set.
Shared strDelimiter As String
Shared intRowsCount As Integer
Public Shared Function getParamValue(ByVal strFileLocation As String, ByVal strFileName As String, ByVal strParamName As String) As String
'Return the value of a specific parameter within the text file
'Return an empty string if param-name is not found
'Return vbNullChar if file was not found
Dim TextLine() As String
Dim strFullFileName As String
If Right(strFileLocation, 1) = "\" Then
strFullFileName = strFileLocation & strFileName
Else
strFullFileName = strFileLocation & "\" & strFileName
End If
getParamValue = ""
If System.IO.File.Exists(strFullFileName) = True Then
If (IsNothing(strDelimiter)) Then strDelimiter = "="
Dim objReader As New System.IO.StreamReader(strFullFileName)
Do While objReader.Peek() <> -1
TextLine = Split(objReader.ReadLine(), strDelimiter)
If (Trim(strParamName) = Trim(TextLine(0))) Then
getParamValue = Trim(TextLine(1))
Exit Do
End If
Loop
objReader = Nothing
Else
MsgBox("File Does Not Exist: " & strFullFileName, MsgBoxStyle.OkOnly, "File Open Error")
getParamValue = vbNullChar
End If
End Function
End Class
End Namespace
This DLL is called: SisConfigTextFiles.dll and is stored in the folder of the executing (calling) (exe) file.
I want to explicitly link to it at runtime, from another Visual Basic application:
Public Class Initializing
Public Const CONFIG_FILE_NAME As String = "AppConfig.ini"
Public Shared Function getConfigParam(ParamName As String) As String
'Load external dll
Dim asm As Assembly = Assembly.Load("SisConfigTextFiles")
Dim type As Type = asm.GetType("TextFiles.ConfigTextFiles")
' Create an instance of a Type by calling Activator.CreateInstance
Dim dynamicObject As Object = Activator.CreateInstance(type)
Dim appPath As String = My.Application.Info.DirectoryPath
getConfigParam = ""
Dim returnValue = DirectCast(type.InvokeMember("getParamValue", _
BindingFlags.InvokeMethod Or BindingFlags.Static, _
Nothing, dynamicObject, {appPath, CONFIG_FILE_NAME, ParamName}), String)
getConfigParam = returnValue
End Function
End Class
However, I keep getting this runtime error:
System.ArgumentNullException: Value cannot be null.
Parameter name: type
Why is "type" Null? How can I straighten this out?
Thanks!

Answer 1

You are almost there but this line isnt valid:
asm.GetType("TextFiles.ConfigTextFiles")
It should be
asm.GetType("SisConfigTextFiles.TextFiles.ConfigTextFiles")
You can see the available types in the Assembly.ExportedTypes property.

Answer 2

Following Sam's advice, here's the fully working code that invokes a method in a DLL with late (run-time) binding:
Imports System.Reflection
Public Class Initializing
Public Const CONFIG_FILE_NAME As String = "AppConfig.ini"
Public Shared Sub Config_Init()
End Sub
Public Shared Function getConfigParam(ParamName As String) As String
'Load external dll
Dim asm As Assembly = Assembly.Load("SisConfigTextFiles")
Dim type As Type = asm.GetType("SisConfigTextFiles.TextFiles.ConfigTextFiles")
' Create an instance of a Type by calling Activator.CreateInstance
Dim dynamicObject As Object = Activator.CreateInstance(type)
Dim appPath As String = My.Application.Info.DirectoryPath
getConfigParam = ""
'Invoking a function "setParamValue" in the dll
Dim returnValue = DirectCast(type.InvokeMember("getParamValue", _
BindingFlags.InvokeMethod Or BindingFlags.Static Or BindingFlags.Public, _
Nothing, dynamicObject, {appPath, CONFIG_FILE_NAME, ParamName}), String)
getConfigParam = returnValue
End Function
End Class