What causes memory fragmentation in .NET

Question

I am using Red Gates ANTS memory profiler to debug a memory leak. It keeps warning me that:

Memory Fragmentation may be causing .NET to reserver too

Answer 1

The .NET Framework 4.5.1, has the ability to explicitly compact the large object heap (LOH) during garbage collection.

GCSettings.LargeObjectHeapCompactionMode = GCLargeObjectHeapCompactionMode.CompactOnce;
GC.Collect();

See more info in GCSettings.LargeObjectHeapCompactionMode