Hi all,
I'm programming a C# application which invokes a DLL (written in standard
C).
I have tried many things but any success since the beginning of the weeks.

Here is the C prototype:

unsigned short GetField ( unsigned short fieldId, char* fieldValue, size_t*
FieldSize);

This method should return a value in fieldValue.

Here is my DLLImport:
[DllImport("reader20.dll", CallingConvention = CallingConvention.StdCall,
CharSet = CharSet.Ansi)]
private static extern ushort GetField (
       ushort fieldId,
       StringBuilder fieldValue,
       out int TailleMax
   );

Here is my call:
int s;
StringBuilder value = new StringBuilder();
SGD_LireChamp(123, value, out s);

I don't understand why "value" still remain to empty string.

Is there something wrong in my code? Do you have any alternative?

Hope someone can help me.
Thanks

Franck

NB:
This DLL can not be modified because it is shipped by a provider.