Using a C# dll inside EXCEL VBA

Question

I am running into a little problem here and need you guys\' help.

I have a C# DLL exposed through COM interop. It is working alright, but apparently the deployment o

Answer 1

You can do that, but you have to be aware of the differences of VBA and .Net.
First, you have to create an actual DLL (.Net assemblies are not), to do that, use this project template. Then again, you have to be aware of how to marshal stuff.
VBA only supports stdcall as calling convention and it can't really deal with Unicode for DLL functions. This isn't bad per se, as the default marshaling for String in .Net is what VBA is expecting (a pointer to an Ansi char). Also, stdcall is the default calling convention that I use for exports.

I'll reuse a sample I've create recently for another SO thread:

Put this in a project you created using my template:

[ComVisible(true), ClassInterface(ClassInterfaceType.AutoDual)]
public class Sample
{
   public string Text
   {
      [return: MarshalAs(UnmanagedType.BStr)]
      get;
      [param: MarshalAs(UnmanagedType.BStr)]
      set;
   }

   [return: MarshalAs(UnmanagedType.BStr)]
   public string TestMethod()
   {
      return Text + "...";
   }
}

static class UnmanagedExports
{
   [DllExport]
   [return: MarshalAs(UnmanagedType.IDispatch)]
   static Object CreateDotNetObject(String text)
   {
      return new Sample { Text = text };
   }
}

This is how to call it from VBA:

Declare Function CreateDotNetObject Lib "The full path to your assembly or just the assembly if it is accessible from Excel" _
  (ByVal text As String) As Object

Sub test()

  Dim instance As Object

  Set instance = CreateDotNetObject("Test 1")
  Debug.Print instance.Text

  Debug.Print instance.TestMethod

  instance.text = "abc 123" ' case insensitivity in VBA works as expected'

  Debug.Print instance.Text
End Sub

Answer 2

These are the using statements to put at the top of your class which are key:

using System.Diagnostics; using RGiesecke.DllExport;

Also ensure that you have a project started before the Nuget PM statement to install the template above. I am new at this - I am sure there are others as well. I am using AutoCAD VBA and got another error since it is 64 bit - I had to use PtrSafe (etc) in the Declare statement for VBA to continue without errors (see MS docs for this http://support.microsoft.com/kb/983043)

It worked btw!

My final code (based on the above)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.InteropServices;
using System.Diagnostics;
using RGiesecke.DllExport;

namespace ClassLibrary3
{
    [ComVisible(true), ClassInterface(ClassInterfaceType.AutoDual)]
    public class Class1
    {
        public string Text
        {
            [return: MarshalAs(UnmanagedType.BStr)]
            get;
            [param: MarshalAs(UnmanagedType.BStr)]
            set;
        }

        [return: MarshalAs(UnmanagedType.BStr)]
        public string TestMethod()
        {
            return Text + "...";
        }
    }

    static class UnmanagedExports
    {
        [DllExport]
        [return: MarshalAs(UnmanagedType.IDispatch)]
        static Object CreateDotNetObject(String text)
        {
            return new Class1 { Text = text };
        }
    }
}

and my vba code:

#If VBA7 Then
    Private Declare PtrSafe Function CreateDotNetObject Lib "G:\gitRepository\VS\ClassLibrary3\ClassLibrary3\bin\Debug\ClassLibrary3.dll" (ByVal text As String) As Object
#Else
    Private Declare Function CreateDotNetObject Lib "G:\gitRepository\VS\ClassLibrary3\ClassLibrary3\bin\Debug\ClassLibrary3.dll" (ByVal text As String) As Object
#End If

Sub test()

  Dim instance As Object

  Set instance = CreateDotNetObject("Test 1")
  Debug.Print instance.text

  Debug.Print instance.TestMethod

  instance.text = "abc 123" ' case insensitivity in VBA works as expected'

  Debug.Print instance.text
End Sub

Answer 3

i had this issue many times. i ended up registering the com dll from vba using a shell and wait method, on the regasm util to register/unregister the dll before late bound creating the com object via

 CreateObject('yourclasshere')

Its a bit of a hack but it works, heres the shellandwait method and a register and unregister method that follows.

             Private Declare Function OpenProcess Lib "kernel32" _
             (ByVal dwDesiredAccess As Long, ByVal bInheritHandle As Long, _
             ByVal dwProcessId As Long) As Long

             Private Declare Function GetExitCodeProcess Lib "kernel32" _
             (ByVal hProcess As Long, lpExitCode As Long) As Long

             Private Const STATUS_PENDING = &H103&
             Private Const PROCESS_QUERY_INFORMATION = &H400


             Private Function ShellandWait(ExeFullPath As String, _
             Optional TimeOutValue As Long = 0) As Boolean

                 Dim lInst As Long
                 Dim lStart As Long
                 Dim lTimeToQuit As Long
                 Dim sExeName As String
                 Dim lProcessId As Long
                 Dim lExitCode As Long
                 Dim bPastMidnight As Boolean

                 On Error GoTo ErrorHandler

                lStart = CLng(Timer)
                 sExeName = ExeFullPath

                 'Deal with timeout being reset at Midnight
                 If TimeOutValue > 0 Then
                     If lStart + TimeOutValue < 86400 Then
                         lTimeToQuit = lStart + TimeOutValue
                     Else
                         lTimeToQuit = (lStart - 86400) + TimeOutValue
                         bPastMidnight = True
                     End If
                 End If

                 lInst = Shell(sExeName, vbHide)

             lProcessId = OpenProcess(PROCESS_QUERY_INFORMATION, False, lInst)

                Do
                     Call GetExitCodeProcess(lProcessId, lExitCode)
                     DoEvents
                     If TimeOutValue And Timer > lTimeToQuit Then
                         If bPastMidnight Then
                              If Timer < lStart Then Exit Do
                         Else
                              Exit Do
                         End If
                 End If
                 Loop While lExitCode = STATUS_PENDING

               ShellandWait = True
               Exit Function

             ErrorHandler:
             ShellandWait = False

             End Function


      Private Function RegisterPayload() As Boolean

          Dim script As String
          script = "cmd /c"
          script = script + " " + "%windir%\Microsoft.NET\Framework\v2.0.50727\regasm"
          script = script + " " + Chr(34) + InstallationPath + Chr(34)
          script = script + " /codebase"

          RegisterPayload = ShellandWait(script)

      End Function

      Private Function UnRegisterPayload() As Boolean
          Dim script As String
          script = "cmd /c"
          script = script + " " + "%windir%\Microsoft.NET\Framework\v2.0.50727\regasm"
          script = script + " " + Chr(34) + InstallationPath + Chr(34)
          script = script + " /u"

          UnRegisterPayload = ShellandWait(script)
      End Function

Hope it helps :)