On: Writing a .NET Garbage Collector in C# – Part 1

[mystified5016]

GC is free to move things all over memory, though I'm not savvy enough to say why this is necessary.

C# allows you to "pin" a variable to combat this. Any pinned memory will never be moved by GC, so if you pass a pointer to an object out of your managed program, the pointer address will always stay valid.

[Dwedit → mystified5016]

If you can't move objects around in memory, you get memory fragmentation.