Question

I am trying to use some pinvoke code to call a C function. The function fills a buffer with data.

The structure is set up as a DWORD for the length, followed by a string. How do I extract the string from the IntPtr?

 IntPtr buffer = Marshal.AllocHGlobal(nRequiredSize);  PInvokedFunction(buffer, nRequiredSize);  string s = Marshal.PtrToStringAuto(buffer + 4); //this is an error.  Marshal.FreeHGlobal(buffer); 

Answer 1

You should do this:

IntPtr sBuffer = new IntPtr( buffer.ToInt64() + 4 ); string s = Marshal.PtrToStringAuto( sBuffer ); 

So your code is 64bit safe.