I managed to make c++ wrapper for VB.NET. However I cannot use it in Excel VBA.
I get an exception File not found related to the VB.NET dll file. However, I’m sure this dll is in current directory, the same where c++ dll is. I also set current directory in
Workbook_Open() event. I watched current directory in c++ dll and it is the one containing VB.NET dll.
Any ideas?

Best regards

public int GetMyStatus(byte[] bName)
{
int status=0;
string strName=”";
System.Text.Encoding encoding = System.Text.Encoding.GetEncoding(“utf-8″);
strName = encoding.GetString(bName);
if(strName==”abc”)
{
status=1;
}
return status;

}

how can I call those two methods from MyDll.dll?

Thanks
Johnson

I’m glad you liked the article. I’m a little unclear on your question though? Can you provide a little more information?

Thanks,
Tom

I have a question here : how to pass parameters from c++ code to call c# method “createMyAccount(byte[] strName)” or “getMyValue(string strName)”

For example.

and in CustomCSharpLib.AddClass,
add two methods,
public void createMyAccount(byte[] strName)
{
…..

}

public int getMyValue(string strName)
{
return 10;
}

Any help?

Thanks

Johnson

Here are the steps I used to return a string:

1) Added the following method to the C# AddClass:

public string GetMsg ()
{
return "Hello, World!";
}


2) Opend MyDll.h and added:

MYDLL_API char* GetMsg();


3) Opened MyDll.cpp and added the following usings:

using namespace System;
using namespace System::Runtime::InteropServices;


4) Added this method to MyDll.cpp:

MYDLL_API char* GetMsg()
{
AddClass addClass;
return (char*) Marshal::StringToHGlobalAnsi(addClass.GetMsg()).ToPointer();
}


5) Opened MyDll.def and added

GetMsg @2


6) Opened CallCSharpCodeSample.cpp and added the following typedef under the original:

typedef char* (WINAPI* LPFN_MSGFUNC)(void);


7) Added the following block of code under the original method call:

LPFN_MSGFUNC getMsg = (LPFN_MSGFUNC)GetProcAddress(hMod, "GetMsg");
if (getMsg != NULL)
{
char* msg = getMsg();
cout << msg << endl;
cout << GlobalFree((HGLOBAL) msg) << endl;
}
else
{
cout << "Failed to load function GetMsg" << endl;
}


Notice the call to GlobalFree? Since I allocated the memory using Marshal.StringToHGlobalAnsi – you have to use GlobalFree to deallocate the memory when your done with the string…

Anyway, like I said – I’m not an expert at this, so this might not be the recommended way of accomplishing this But, it seems to work ok.

This is an excellent article for calling the managed C# dll from C application.

I have a question regarding the passing C# string back to C function caller.
In C, I’d like to get a string stored in Managed C# dll to display in C, how do I do that?

For example, in your MyDll.dll,
Add one function,

void GetmyMessage(char* myMsg)
{
AddClass addClass;
addClass.GetMyMessage(myMsg);

}

and in CustomCSharpLib.AddClass,
add one method,
public void GetMyMessage(ref byte[] strMsg)
{
string MyMsg = “Hello.”;
strMsg = Encoding.ASCII.GetBytes(MyMsg);

}

Any help?

Thanks

Wayne

The VB dll needs to be either in the GAC, or in the same directory as MyDll.dll. So, you will need to have at minumum:

TheApplication.exe
MyDll.dll
VBCodeLib.dll

All in the same directory.
HTH

Fixed the problem. Thanks a lot for your help!