http://blogs.msdn.com/b/cgarcia/archive/2011/06/15/interop-marshaling-double-pointers-that-can-be-null.aspxI recently had to implement IMediaBuffer in managed code. The GetBufferAndLength method takes a BYTE** ppBuffer argument, so I initially went with the following straightforward C# declaration: public void GetBufferAndLength( out IntPtr ppBuffer, outen-USTelligent Evolution Platform Developer Build (Build: 5.6.50428.7875)