How did dobby died in Harry Potter?

Answer 1

Dobby does not die in Book 6, he dies in Book 7 while helping Harry, Ron and Hermione escape from Malfoy Manor where they were held captive for a short while and Hermione was tortured by Bellatrix Lestrange. It was Bellatrix who killed Dobby, she tried to kill Harry but she hit Dobby by throwing a dagger at him when he was apparating the three out of there. It hit Dobby instead and Harry buried him at Bill and Fleur's cottage without magic, which Griphook the goblin cannot understand.

Griphook the goblin was captured and taken to Malfoy Mannor, with the three, and Dean. Luna and Mr Ollivander the wand maker were already there and had been for a while. Dobby disapparated Luna, Ollivander and Dean first, then returned for Hermione, Ron, Harry and the goblin. Harry insisited on leaving together and not leaving anyone behind. Which the goblin also saw as strange.

Answer 2

Dobby died to save Harry in the Malfoy Mansion

When Harry, Ron, Hermione, Luna, Gregorovich, Griphook was caught by the Death eaters, Dobby teleports to them and sends Gregorovich and Luna to where Bill lives. However, after Harry, Ron, and Hermione is together, DObby comes and tries to save them by teleporting to Bill's place. But he wasnt so lucky because at the moment they were teleporting, Bellatrix threw a silver dagger which stroke at dobby's heart. All of them teleported, but dobby had a dagger on his heart.