This thread is for discussions of Hosting Control Panel Applets using C#/C++.

This article is very useful to understand how to call unmanaged function from C#.net. I have to do the same thing for my project but it seems little complex as it is passing user defined data type as an argument to the calling function. I will appreciate help with this.
Unmanaged C++ function which I am trying to call from C#.net app. is as below: (from the header file)

static void LibAction(const libString& actionXML, libString& returnXML, libError& libError);

libSting is a reference to the container class - wraps Standard Teplate Library String type. declared in the header file as below:

class LIB_CLASS_EXPORT LibString : public std::string
{
 typedef std::string STL_STRING;
public:

 // --- Constructors/Destructor ---
 
 LibString() { ; }
 LibString(const LibString& S);
 LibString(const char* s);
 LibString(char s);
 LibString(istream&);
 LibString(const STL_STRING & S) : STL_STRING(S) { ; }
 virtual ~LibString();


libError is a reference to the container class which is used for the error handling.

How do I call this function from C# windows application.

Below is how I am trying to declare above function in my C# app.

[DllImport(@"C:\Test\dlls\Lib.dll", EntryPoint="LibAction")]
public static extern void LibAction(string actionXML, string returnXML, string libError);

Instead of string I should be passing ref to the libString. I am not sure how do I do that in C#.

Please help.

Sorry, I had a comment, but it was a mis-understanding of the original post.

Hi,

have also tried to convert the ambigous #define MAKEINTRESOURCEW(i) (LPWSTR)((ULONG_PTR)((WORD)(i))) in C++ into C# but with no luck.
So I compiled a C++ program using MAKEINTRESOURCE and traced it to see what TYPE is really passed to UpdateResource(..) or similar resource accessing functions. What I hav efound that it actaully passes the interger value (Resource ID). For example if you have a Resource with "MY_RES_ID" with ID 129
the compiled code actaully just passes the 129 as a WORD data.

So in C# while doing DllImport, I just chaged the Data Type for the Resource Id parameter which uses MAKEINTRESOURCE.
Here is what I did with UpdateResource

[DllImport("kernel32.dll")]
static extern bool UpdateResource(IntPtr hUpdate, string lpType, int lpName,  ushort wLanguage, IntPtr lpData, uint cbData);

Notice the Third param which has been chaged from String to int. And It works!!!  Now you will just pass (using my example as mentioned above) 129 instead of MY_RES_ID, or directly MY_RES_ID if it is defined somewhere to reprent 129.



----
Rezaul Kabir
shuvro@yahoo.com