I’d google C++ Pointers and give yourself a quick tutorial of them.
The C# version of:
SendPacket MyPacket = new SendPacket();
Under the hood, that line is actually this (which is the proper C++ version):
SendPacket* MyPacket = new SendPacket();
C# hides pointers / memory management from you. Read through pointers real quick on whatever tutorial website you can find and things should make more sense.