What is the situational irony and dramatic irony in "The Necklace"?

Situational irony is, simply put, when the opposite of what one expects to happen occurs.  In "The Necklace," Guy de Maupassant relies once again on his dark situational irony to end the story and advance his theme.  At the end of the story, Mathilde who despises hard labor and anything unglamorous discovers that she has sacrificed the best years of her life to replace a necklace that she discovers is a fake.  Someone who prided herself in such taste and appearance could not even tell the difference between the artificial and valuable.

While this story does not have much dramatic irony, de Maupassant does include some in that Madame Forestier knows all along that the necklace is not real and chooses not to tell Mathilde earlier.  Thus, a character in the story is privy to information that another character does not know.