Why would want to know? Is there any specific requirement? The
information can be obtained by using the CLR Hosting interface
ICLRGCManager::GetStats  which returns

typedef struct _COR_GC_STATS {
   ULONG   Flags;
   SIZE_T  ExplicitGCCount;
   SIZE_T  GenCollectionsTaken[3];
   SIZE_T  CommittedKBytes;
   SIZE_T  ReservedKBytes;
   SIZE_T  Gen0HeapSizeKBytes;
   SIZE_T  Gen1HeapSizeKBytes;
   SIZE_T  Gen2HeapSizeKBytes;
   SIZE_T  LargeObjectHeapSizeKBytes;
   SIZE_T  KBytesPromotedFromGen0;
   SIZE_T  KBytesPromotedFromGen1;
} COR_GC_STATS;

You can get watch the Gen0, 1, 2 and large object heap sizes from the "CLR
memory" performance counters using perfmon, or from code by using the
System.Diagnostics.Performance class.

Willy.

I tried another approach and it did work for me, that's monitoring how many
bytes are allocated before and after the garbage collector cycle.
Thanks,
   Ravi.