Since .NET has a garbage collector why do we need finalizers/destructors/dispose-pattern?

Question

If I understand correctly the .net runtime will always clean up after me. So if I create new objects and I stop referencing them in my code, the runtime will clean up those

Answer 1

Because the the Garbage Collector cannot collect what the managed environment did not allocate. Therefore any call to an unmanaged API that results in a memory allocation needs to be collected in the old fashioned way.