Returning a string from a C++ dll

could you show us your code atleast so that others can get idea.

thanx
Paresh

Yep, it's pretty straightforward when you know how.

Here's the C# method:

public unsafe void GetString( sbyte* String )
{
string TestString = "Hello World";

// Convert string to unsafe pointer
char[] CharArray = new char[TestString.Length];
CharArray = TestString.ToCharArray();

foreach ( char Char in CharArray )
{
*String++ = (sbyte)Char;
}

// Add terminating null
*String = (sbyte)'\0';
}

and the C/C++ code to call it:

char String[30];
GetString( String );

Hope that helps (obviously need to check for string overflow)

Sarah ;)

thanks...;)

Hi guys,
Interesting thread. I have same problem, but I have exported function which I cannot change. The declaration is:
short MyFunc(TCHAR* cRefNumber);
and the export is defined in the *.def file.

And your advice does not work with this scenario. I got the error below on the line MyString = Marshal.PtrToStringUni(ptr);
“An unhandled exception of type ‘System.NullReferenceException’ occurred in mscorlib.dll”.
:confused:

Could you help me, please?
Btw: I am new in .NET and C#.

Thanks,
David

to me it looks like you haven't initialized the string.

paresh

I initialized the string.
I think the main difference is between declartions of exported function. GMV’s solution contains two pointers, but I have only one:
GetStringFromDLL(WCHAR** ppString);
MyDLLFunc(TCHAR* pszRefNumber);
But I cannot change it.

thanks anyway,
David

Hello Experts,

I also have some problems related to string ...
Sorry for posting this question again ...

I want to use a function written in C++ VS6.0 dll.
The function takes "CString&" as an argument.
I want to call this function from a Managed C++ dll.

// .....
CString strTest;
CString strTest1;

SomeFnInVC6( strTest );
strTest1 = strTest; // ----->>> Exception here !!!
// ....


Is it possible to do like this ? Please give me a solution.
Thanks.