64-bit App doesn't work with COM?

Hi, I have an Web-App and inside use I COM DLL(C# class library). This DLL tested I in debug mode in VS2015 for AnyCPU and too for x64. The 32-bit Web-App works with the both DLLs fine. When I compile the Web-App as 64-bit and I run it through then Windows write Application stopped working (Close/Debug). When I clicked on debug so it transfer me into VS2015, but there is nothing to see.
Do you think, it is any bug in 64-bit Web-App? Or 64-bit Web-App can’t work with COM objects? Or do you know, what can I with that do?

Post the code you are using to call the DLL please.

The COM object needs to be 64-bit as well.

Hi Michel,
in Xojo is to call DLL:

[code] dim actualCS as string
dim HelperLib as new SRMXOJO.SRMUtils
actualCS= HelperLib.GetConnectionString(datapool) //DLL call I here
dim CSarray() as string
dim helpArray() as string
dim helpArray2() as string
dim ERPdbType, SRMdbType as string

CSarray = actualCS.Split("//")
actConnectionString = new ConnectionStrings
actConnectionString.DataPoolName = datapool


In C# is:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using SRM.SRMHelperLib;
using System.Windows.Forms;
using System.Runtime.InteropServices;

namespace SRMXOJO.SRMHelperLib
    public interface SRMUtilsInt {
        string GetConnectionString(string DataPool);
        string GetDatapoolName();
    public class SRMUtils : SRMUtilsInt
        public string GetConnectionString(string DataPool)
        public string GetDatapoolName()

Have you tested C# in 64 bit ? Are you sure the DLL is 64 bit ready ?