Problem with P/Invoke

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C#

.NET

PInvoke

Hi I have written a code in C# to load functions in an unmanaged dll.
This is the code.

class Program
 {
     static unsafe void Main(string[] args)
     {
         int deviceNr;
         char* Info;
         int intMyReturnVal;
         deviceNr = 0;
         Info = null;
         intMyReturnVal = sample_getinfo(deviceNr, Info);
     }

     [DllImport("opcard2lib.dll")]
     private unsafe static extern int sample_getinfo(int deviceNr, char* Info);
 }

and this is the API function description by dll supllier.

1. Sample_GetInfo

Prototype:
DLLReturnType
Sample_GetInfo (int deviceNr,
char* Info);

Parameters:
deviceNr is a number of found card in system
Info is handler for string with information about current card in system

Returns:
Returns 0 (zero) when success. Otherwise return an error code.

Description:
This function provide information about installed card in system. Information returned
in Info string looks like below:
„SN YY.SN rev. RRR", where:
YY – year of production
SN – serial number
RRR – firmware revision

The problem is that when I run this code I get the bellow error exception:
Attempted to read or write protected memory. This is often an indication that other memory is corrupt.

I have written this in VB.net to and get the same result.
I would appreciate your help.